Publications 2020

Chih‐Chien Lee, Richie Estrada, Ya‐Ze Li, Sajal Biring, Nurul Ridho Al Amin, Meng‐Zhen Li, Shun‐Wei Liu, Ken‐Tsung Wong

Efficient and vacuum‐processed small molecular organic photodetectors (OPDs) employing the active layer of ClAlPc: C 70 have been demonstrated by Shun‐Wei Liu, Ken‐Tsung Wong and co‐workers, as reported in article number 2000519. Such proposed OPDs with low dark current density (1.15× 10− 9 A cm− 2), high rising/fall time (< 2 μs), wide optical power range (linear dynamic range of> 173 dB), and strong response (0.439 AW− 1 at− 2.0 V) to near‐infrared wavelength (730 nm) open up the possibility of their successful application in optical (Li‐Fi) communication, artificial vision, biomedical detection, etc. ...Read More

Anand Sharma, Nitesh K Chourasia, Vishwas Acharya, Nila Pal, Sajal Biring, Shun-Wei Liu, Bhola N Pal

Low surface-roughness and high-capacitance ion-conducting LiAlO2 gate dielectric thin film has been fabricated by sol–gel technique to develop ultra-low voltage (≤ 1.0 V) indium-zinc-oxide thin film transistor (TFT). This LiAlO2 dielectric shows α-LiAlO2 and γ-LiAlO2 phases those have been fabricated at two different temperatures. For both phases, mobile Li-ion is responsible to achieve a high dielectric constant (κ) of the material that helps to reduce the operating voltage of TFT. Additionally, lower surface roughness of LiAlO2 thin film creates a low-density trap state in the..Read More

Miaosheng Wang, Ya-Ze Li, Hung-Cheng Chen, Che-Wei Liu, Yi-Sheng Chen, Yuan-Chih Lo, Cheng-Si Tsao, Yu-Ching Huang, Shun-Wei Liu, Ken-Tsung Wong, Bin Hu

This paper demonstrates high-efficiency organic near-infrared (NIR) photodetection activities by increasing the symmetry of photoinduced charge density based on planar cyclic donor-acceptor structures. The record-high photosensing capability (gain: 3x105 and EQE: 43 % at 3 V) is realized under the NIR 780 nm illumination upon using the single-component active layer chloroaluminum phthalocyanine (ClAlPc) with planar cyclic intramolecular donor-acceptor structures to create four-fold symmetry of photoinduced charge density. Our in-situ measurement of using bias-dependent magneto-photocurrent reveals that increasing the symmetry..Read More

Chih‐Chien Lee, Richie Estrada, Ya‐Ze Li, Sajal Biring, Nurul Ridho Al Amin, Meng‐Zhen Li, Shun‐Wei Liu, Ken‐Tsung Wong

A near‐infrared photodetector with optimized performance is reported using varied thickness (20, 40, 60, and 80 nm) of the active layer comprising chloroaluminium phthalocyanine (ClAlPc) and fullerene (C70) at the ratio of 1:3, and TAPC:10% MoO3 and BPhen as electron and hole blocking layers, respectively. The experimental results reveal that the photodetector with 80 nm thick active layer provides the best performance at the wavelength of 730 nm achieving a very low dark current density of 1.15 × 10−9 A cm−2 and an external quantum efficiency of 74.6% with a responsivity of 0.439 A W−1 at −2 V bias. Additionally, the device exhibits a dramatic high detectivity of 4.14 × 1013 cm Hz1/2 W−1 at 0 V bias. The device exhibits not only a large linear response over a wide optical power range (LDR of 173.0 dB), but also a broad frequency response (778.7 kHz) and rise/fall time of 2.13/0.77 µs (based on trigger …..Read More

Chun‐Kai Wang, Xiaozhou Che, Yuan‐Chih Lo, Ya‐Ze Li, Yung‐Hao Wang, Stephen R Forrest, Shun‐Wei Liu, Ken‐Tsung Wong

Four new donor‐acceptor‐acceptor’ (D‐A‐A’)‐configured donors, CPNT, DCPNT, CPNBT, and DCPNBT equipped with naphtho[1,2‐c:5,6‐c′]bis([1,2,5]‐thiadiazole) (NT) or naphtho[2,3‐c][1,2,5]thiadiazole (NBT) as the central acceptor (A) unit bridging triarylamine donor (D) and cyano or dicyanovinylene acceptor (A’), were synthesized and characterized. All molecules exhibit bathochromic absorption shifts as compared to those of the benzothiadiazole (BT)‐based analogues owing to improved electron‐withdrawing and quinoidal character of NT and NBT cores that lead to stronger intramolecular charge transfer. Favorable energy level alignments with C70, together with the good thermal stability and the antiparallel dimeric packing render CPNT and DCPNT suitable donors for vacuum‐processed organic photovoltaics (OPV)s. OPVs based on DCPNT : C70 active layers displayed the best power conversion …..Read More

Zhen-Jie Gao, Tzu-Hung Yeh, Jing-Jie Xu, Chih-Chien Lee, Anuradha Chowdhury, Bo-Cheng Wang, Shun-Wei Liu, Chih-Hsin Chen

A series of carbazole/benzimidazole-based molecules, namely, o-CbzBiz, m-CbzBiz, and p-CbzBiz, were readily synthesized in three steps by integrating carbazole with benzimidazole via the ortho-, meta-, and para-positions of phenyl linked to N-phenyl carbazole. These bipolar molecules exhibited a maximum UV absorption band ranging from 310 to 327 nm and a maximum emission band ranging from 380 to 400 nm. Density functional theory calculations showed that the twist angles between the donor and acceptor moieties of these molecules were from 54.9 to 67.1°. Such a twisted structure hampered the π-electron conjugation within the molecule and resulted in high-lying LUMO levels and triplet energies, which make them suitable to be applied as host materials in OLED devices. Our results showed that a maximum external quantum efficiency (EQE) of OLED reached 21.8% when p-CbzBiz was applied as …..Read More

Nurul Ridho Al Amin, Kiran Kishore Kesavan, Sajal Biring, Chih-Chien Lee, Tzu-Hung Yeh, Tzu-Yu Ko, Shun-Wei Liu, Ken-Tsung Wong

An efficient organic light-emitting diode based on the BCzPh:CN-T2T exciplex as an emitting layer (EML) has been fabricated by exploiting charge balance and favorable molecular orientations. To further understand the details of the exciplex-forming mechanism, time-resolved photoluminescence (TRPL), capacitance-voltage (CV), impedance spectroscopy (IS), and transient electroluminescence (EL) measurements were used to probe the photophysical and electrical characteristics of EL devices by incorporating interfacial (BCzPh/CN-T2T) and bulk (BCzPh:CN-T2T) exciplexes as the emitting layer. Interfacial- and bulk-exciplex devices exhibit a maximum external quantum efficiency (EQE) of 7.7 and 26.4%, respectively. The reason for different device performances was rationalized by comparing the accumulated amount of charge density at the EML’s interface responsible for exciplex emission. In addition, the …..Read More

Shun-Wei Liu, Chih-Chien Lee, Sajal Biring

This Conference Presentation, Highly efficient, transparent, and near-infrared organic up-conversion devices, was recorded at Photonics West 2020, San Francisco, United States..Read More

Yan-Zhi Chen, Dian Luo, Chi-Haw Hsiang, Rong-Huei Yi, Ching-Hsuan Lin, Chin-Wei Lu, Shun-Wei Liu, Chih-Hao Chang, Hai-Ching Su

Enhancing device efficiencies of the blue and white light-emitting electrochemical cells (LECs) is realized by employing substrates with embedded diffusive layers containing scattering TiO2 nanoparticles (NPs). The diffusive layers can eliminate the influence of microcavity effect on the output electroluminescence (EL) spectrum and recover the intrinsic EL spectrum of the emissive layer. The emission zone positions of the blue and white LECs are estimated by fitting the measured EL spectra with the simulated EL spectra based on precisely tuned emission zone positions. Incorporating red-emitting guest dopant in the white LEC results in shifted emission zone toward the cathode due to enhanced electron trapping. The external quantum efficiency (EQE) of the blue and white LECs employing proper diffusive substrates can be enhanced by 260 and 210%, respectively. The maximal EQE (power efficiency) of the blue …..Read More

Miaosheng Wang, Ya-Ze Li, Hung-Cheng Chen, Che-Wei Liu, Yi-Sheng Chen, Yuan-Chih Lo, Cheng-Si Tsao, Yu-Ching Huang, Shun-Wei Liu, Ken-Tsung Wong, Bin Hu

This paper demonstrates high-efficiency organic near-infrared (NIR) photodetection activity by increasing the symmetry of photoinduced charge density based on planar cyclic donor–acceptor structures. The record-high photosensing capability (gain: 3 × 105 and EQE: 43% at 3 V) is realized under NIR 780 nm illumination upon using the single-component active layer chloroaluminum phthalocyanine (ClAlPc) with planar cyclic intramolecular donor–acceptor structures to create four-fold symmetry of photoinduced charge density. Our in situ measurement using bias-dependent magneto-photocurrent reveals that increasing the symmetry of photoinduced charge density through planar cyclic intramolecular donor–acceptor structures can significantly decrease the electron–hole binding energies, allowing the direct generation of free photogenerated carriers without any heterojunction structures. Particularly, with the four …..Read More

Anand Sharma, Nitesh K Chourasia, Vishwas Acharya, Nila Pal, Sajal Biring, Shun-Wei Liu, Bhola N Pal

Low surface-roughness and high-capacitance ion-conducting LiAlO2 gate dielectric thin film has been fabricated by sol–gel technique to develop ultra-low voltage (≤ 1.0 V) indium-zinc-oxide thin film transistor (TFT). This LiAlO2 dielectric shows α-LiAlO2 and γ-LiAlO2 phases those have been fabricated at two different temperatures. For both phases, mobile Li-ion is responsible to achieve a high dielectric constant (κ) of the material that helps to reduce the operating voltage of TFT. Additionally, lower surface roughness of LiAlO2 thin film creates a low-density trap state in the semiconductor/dielectric interface which is capable to reduce operating voltage within 1.0-volt. The device with 700 °C annealed γ-LiAlO2 gate dielectric shows the best device performance with an electron mobility of 25 cm2 V−1 s−1 and an on/off ratio of 3 × 105. Instead, 350 °C annealed α-LiAlO2 dielectric require only one volt to …..Read More

Addanki Venkateswararao, Johnny KW Ho, Shu Kong So, Shun-Wei Liu, Ken-Tsung Wong

Indoor photovoltaics (IPVs), which convert the indoor light energy into direct electricity, have attracted research attention due to their potential use as an excellent amicable solution of sustainable power source to drive low-power-needed sensors for the internet of things (IoT) applications. Our daily life adopts various indoor light sources, such as indirect sunlight, incandescent lamps, halogen lamps, fluorescent lamps, and LED bulbs, that typically deliver lower light intensity (200–1000 lux) as compared to that of sun light (∼100,000 lx). In this review, we firstly classified the indoor lights depending on their working mechanism and resulting emission spectrum. Because the indoor light intensities are rather low that may lead to overestimate/underestimate the power conversion efficiency (PCE) of IPV devices, then, the cautious points for correctly measuring the indoor light intensity as well as the device characteristics …..Read More

Satya Veer Singh, Anand Sharma, Sajal Biring, Bhola N Pal

A new method has been developed to grow copper (I) sulfide (Cu2S) nanoparticle (NP) inside a titanium dioxide (TiO2) thin film. This Cu2S NP growth process consists of two successive steps: ion-exchange and sulfurization process. In the beginning, Li4Ti5O12 thin film has been fabricated by a sol-gel process that contains mobile lithium-ion (Li+). This ion-conducting Li4Ti5O12 thin film has been deposited by spin coating and subsequent annealing method. In the following step, Li+ has been exchanged with Cu+ by the ion-exchange method that has been converted to Cu2S by subsequent sulfurization process. The ion-exchange has been done by immersing this Li4Ti5O12 thin film into a copper (I) chloride (CuCl) solution, whereas sulfurization has been done by dipping the Cu+ contain thin film within aqueous sodium sulfide (Na2S) solution. This process allows us to fabricate smooth and large area TiO2 thin …..Read More

Nitesh K Chourasia, Anand Sharma, Nila Pal, Sajal Biring, Bhola N Pal

Herein, dielectric/semiconductor interfacial p‐doping is used to develop a high‐carrier‐mobility and balanced ambipolar tin oxide (SnO2) thin‐film transistor (TFT). To introduce this interfacial doping, TFTs are fabricated by using two different ion‐conducting oxide dielectrics containing trivalent atoms. These ion‐conducting dielectrics are LiInO2 and LiGaO2 containing a mobile Li+ ion that reduces the operating voltage of these TFTs to ≤2.0 V. During SnO2 thin film deposition, the interfacial SnO2 layer is p‐doped by an In or Ga atom of the gate dielectric and therefore, hole conduction is facilitated in the channel of the TFT. To realize this interfacial doping phenomenon, a reference TFT is fabricated with a Li2ZnO2 dielectric that contains a divalent zinc atom. Comparative electrical data indicate that TFTs with LiInO2 and LiGaO2 dielectrics are ambipolar in nature, whereas the TFT with a Li2ZnO2 dielectric is a …..Read More

Nasima Khatun, Saurabh Tiwari, Ruhul Amin, Chuan-Ming Tseng, Sajal Biring, Somaditya Sen

A series of charge compensated Ga–V co-doped TiO2 samples (Ti(1-x)(Ga0.5V0.5)xO2) have been synthesized by a modified sol-gel process. X-ray diffraction pattern shows that the anatase to rutile (A→R) onset temperature (TO) shifts to a higher temperature, whereas the complete phase transformation temperature (TC) shifts to a low-temperature region as compared to pure TiO2, due to Ga–V incorporation. Ga–V co-doping helps in the transformation of some smaller sized Ti4+ to a relatively larger Ti3+. In the anatase phase, oxygen content also increases with increasing doping concentration, which along with the larger size of Ti3+ results in lattice expansion and thereby delays the TO. In the rutile phase, oxygen vacancy increases with increasing doping concentration, which results in lattice contraction and accelerates phase transition. Grain growth process is hindered in the anatase phase (crystallites size …..Read More

Nitesh K Chourasia, Anand Sharma, Nila Pal, Sajal Biring, Bhola N Pal

p-type doping from the dielectric/semiconductor interface of a SnO2 thin film transistor (TFT) has been utilized to develop high carrier mobility balanced ambipolar oxide-transistor. To introduce this interfacial-doping, bottom-gate top-contact TFTs have been fabricated by using two different ion-conducting oxide dielectrics which contain trivalent atoms. These ion-conducting dielectrics are LilnO2 and LiGaO2 respectively, containing mobile Li+ ion. During SnO2 thin film fabrication on top of the ionic dielectric, those trivalent atoms allow p-doping to the interfacial SnO2 layer to introduce the hole conduction in channel of TFT. To realize this interfacial doping phenomena, a reference TFT has been fabricated with Li2ZnO2 dielectric under the same condition that contains divalent zinc (Zn) atom. Our comparative electrical data indicates that TFTs with LilnO2 and LiGaO2 dielectric are ambipolar in nature whereas, TFT with Li2ZnO2 dielectric is a unipolar n-channel transistor which reveals the interfacial doping of SnO2. Most interestingly, by using LilnO2 dielectric, we are capable to fabricated 1.0 V balanced ambipolar TFT with a high electron and hole mobility values of 7 cm2 V-1 s-1and 8 cm2 V-1 s-1 respectively with an on/off ratio> 102 for both operations which has been utilized for low-voltage CMOS inverter fabrication...Read More

Vivek Parimi, Sajal Biring, Ku Chia Hao, Abhirup Datta, Somaditya Sen

In this paper, a novel dielectric resonator antenna has been numerically simulated and experimentally demonstrated. The proposed design, comprising an Indium Tin Oxide (ITO) coated glass slide placed on a microstrip transmission line, is intended for WLAN and Wi-Max applications. The antenna shows a maximum bandwidth of 2.15-7.65 GHz and 10.36-11.78 GHz and a gain ranging from 2.21 to 6.44 dB. The novelty of the design lies in the use of ITO coating on glass to enhance as well as regulate the antenna bandwidth. Parametric variations have been investigated to analyse the topology for understanding the effect of the design parameters on gain, bandwidth, and reflection coefficient. A prototype has also been fabricated, where different ITO sheets have been mounted to measure the response. The proposed geometry has been found to be better and competent enough with respect to antenna parameters …..Read More

Lung-Chien Chen, Ching-Ho Tien, Po-Wei Tseng, Zong-Liang Tseng, Wei-Lun Huang, You-Xun Xu, Hao-Chung Kuo

In order to improve the stability and cost of perovskite CsPbBr3 and establish a preparation process for quantum dot materials with excellent luminescence properties, CsPbBr3 quantum dots were synthesized by the hot injection method and the ice bath method in air ambient. Then, a proprietary purification system was used to improve the properties of the quantum dots and prepare high-quality perovskite quantum dot films. Optimal material and light characteristics were exhibited with ethyl acetate:hexane as the purification solvent. In the solution form, the photoluminescence wavelength could be maintained at 508 nm with almost no shift compared with other conditions, and the quantum yield could reach 99%; however, superior performance was obtained in the thin-film form, which exhibited little to no shift in the photoluminescence wavelength and, surprisingly, achieved a quantum yield of 91.6% with a narrow …..Read More

Chun-Cheng Lin, Lung-Chien Chen, Ching-Ho Tien, Bo-Quan Chen, Zong-Liang Tseng

In this paper, a dimethyl sulfoxide (DMSO) bathed poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS, 1: 1.25) film served as the transparent conductive layer (TCL) and the undoped PEDOT: PSS (1: 6) film was used as the hole transport layer (HTL) of methylammonium lead iodide (MAPbI 3) perovskite solar cells (PSCs). Optimal performances (ie an open circuit voltage of 0.67 V, a short circuit current density of 20.1 mA cm− 2, a fill factor of 51.8%, and a power conversion efficiency of 8.96%) of the PSC were achieved by a two-layer TCL and HTL...Read More

Zong-Liang Tseng, Chien-Hung Chiang, Chun-Guey Wu

Perovskite solar cells (PSCs) are one of the highly promising new‐generation photovoltaic technologies. One of the remaining challenges for commercializing PSCs is to prepare high‐quality, large‐area perovskite films in an ambient atmosphere reproducibly using less toxic materials. Herein, a nonvolatile, less toxic substance, 2‐pyrrolidinone (2P), is used as a complexant solvent for the perovskite precursor solution. Combining this with a newly developed spin‐assisted solvent extraction (SASE) crystallization method, a high‐quality perovskite film is prepared in air reproducibly. The nonvolatile nature of 2P and the formation of MAI–PbI2–2P adduct widen the time window for antisolvent engineering, and SASE enhances the solvent exchange rate of the precursor film to form a high‐quality perovskite film in air. An inverted cell (based on the postsolvent‐treated perovskite absorber) exhibits a power conversion …..Read More

HP Hsu, DY Lin, CW Chen, YF Wu, K Strzałkowski, P Sitarek

Cadmium zinc telluride is a tunable band gap II–VI compound semiconductor, which has received considerable attention due to its applications such as nuclear radiation detectors and industrial process monitoring. We have studied the optical properties of the ternary compound semiconductors Cd1−xZnxTe grown by vertical Bridgman-Stockbarger method in the whole range of zinc content 0 < x < 1. The crystal structure and material phase were characterized by X-ray diffraction (XRD) and Raman spectra. We measured the band gap energy for each of the samples by absorption and photoluminescence (PL) spectroscopy. From the experimental results we found that the band gap energy of Cd1−xZnxTe was located at around 1.457 eV with x = 0, and gradually shift to 2.174 eV for x equal to 1. The temperature-dependent absorption measurements to study the temperature dependence of band gap energy were also …..Read More

Chih-Ping Chen, Bing-Huang Jiang, Ping-Hung Chan, Yu-Wei Su, Hsiang-Lin Hsu, Ru-Jong Jeng

In this study we used p-type [poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and nickel oxide] and n-type (sol–gel and nanoparticle zinc oxides) materials as transporting layers for PM6:Y6–based organic photovoltaic (OPV) devices. These solution-processed transporting layers exhibited various surface energies, morphologies, and roughnesses that affected the subsequent growth of PM6:Y6 blend films. Using atomic force microscopy and grazing-incidence wide-angle X-ray spectroscopy, we observed various PM6:Y6 blend film morphologies on the different substrates. Furthermore, the surface-induced PM6:Y6 blend morphology influenced the mechanism of carrier recombination and, thereby, affected the device performance. Among our tested systems, the PEDOT:PSS–based devices exhibited superior surface properties, possessed larger phase-segregated domains, and featured strong …..Read More

Bing-Huang Jiang, He-En Lee, Jong-Hong Lu, Tsung-Han Tsai, Tien-Shou Shieh, Ru-Jong Jeng, Chih-Ping Chen

In this study, we designed a surface phase-matched transmission enhancement (PTE) top electrode–Ag/indium tin oxide (ITO) structure for highly efficient and aesthetic semitransparent organic photovoltaics (ST-OPVs). The purposed highly transparent back electrodes (Ag/ITO) could selectively decrease visible reflection and increase transparency accordingly. By altering the thicknesses of the Ag and ITO layers, we could control the transmittance curve and increase the transparency of the ST-OPV devices. Devices based on PTB7-Th:IEICO-4F and PM6:Y6:PC71BM displayed outstanding performance (8.1 and 10.2%, respectively) with high visible light transmittance (36.2 and 28.6%, respectively). The outstanding visible and near-IR light harvesting of PM6:Y6:PC71BM further allowed a new application: double-sided energy harvesting from solar and indoor illumination. The simple optical design of a top electrode …..Read More

Kai-Ting Huang, Chih-Ping Chen, Bing-Huang Jiang, Ru-Jong Jeng, Wen-Chang Chen

In this study, we first revealed a green material-Poly-lysine as an interfacial layer (IFL) of electron-extraction layer (EEL) and investigated evolution of morphologies of the active layers in organic photovoltaics (OPVs). The surface structure of the active layers was characterized by atomic force microscopy (AFM) and the molecular packing features were revealed by grazing-incidence wide-angle X-ray scattering (GIWAXS). By embedding poly-lysine as IFL, we evidenced the changes of the blend film phase segregation and observed an increase order of molecular packing in preferential face-on orientation. The optimized blend film morphology facilitated the carrier extraction, thereby significantly improved the OPV performance with the best power conversion efficiency (PCE) of 12.5% and 15.3% for the PBDB-T-2Cl:IT-4F and PBDB-T-2F:Y6 blends, respectively. Compared with the controlled devices, the poly-lysine …..Read More

Er-Chieh Cho, Cai-Wan Chang-Jian, Jen-Hsien Huang, Guang-Yu Lee, Wei-Hung Hung, Ming-Yen Sung, Kuen-Chan Lee, Huei Chu Weng, Wei-Lin Syu, Yu-Sheng Hsiao, Chih-Ping Chen

In this article, we have synthesized Co2+-doped BiOBrxCl1-x hierarchical nanostructured microspheres, featuring different degrees of Co2+ doping, displaying excellent photocatalytic performance. X-ray diffraction and Raman spectroscopy indicated that the Co2+ ions were successfully doped into the BiOBrxCl1-x nanocrystals. The photodegradation rate of rhodamine B mediated by a doped BiOBrxCl1-x was 150 % greater than that of the non-doped BiOBr. We ascribe the improved photocatalytic capability of the Co2+-doped BiOBrxCl1-x to a combination of its superior degree of light absorption, more efficient carrier separation, and faster interfacial charge migration. The major active species involved in the photodegradation of RhB also has been investigated. Moreover, the doped BiOBrxCl1-x possessed excellent cellular biocompatibility and displayed remarkable performance in the photocatalytic bacterial …..Read More

Bing-Huang Jiang, Chih-Ping Chen, Hsin-Te Liang, Ru-Jong Jeng, Wen-Chen Chien, Yang-Yen Yu

The recent use of non-fullerene materials has significantly increased the efficiency of organic photovoltaic (OPV), with ternary OPVs providing an effective means of further enhancing the performance. In this study, we evaluated the role played by the small molecule Y6 as the third component in additive-free PM6 (polymer): Y6:IT-4F (small molecule) ternary OPVs. We used UV–Vis spectroscopy, photoluminescence spectroscopy, and tapping-mode atomic force microscopy to study the effects of various blend ratios on the optoelectronic properties of these OPVs. At the optimized PM6:Y6:IT-4F blend ratio (1:0.35:0.75), we observed the presence of Y6:IT-4F intermediates that efficiently suppressed the over-segregation of Y6 and increased the degree of carrier transport. The optimized ternary OPV delivered an average power conversion efficiency (PCE) of 13.6 ± 0.29% and the best PCE of 14.14%, which was 23 …..Read More

Hsiang-Lin Hsu, Bing-Huang Jiang, Chung-Lin Chung, Yang-Yen Yu, Ru-Jong Jeng, Chih-Ping Chen

Commercially available Jeffamines (polyetheramine) with average molecular weights of 2000 and 3000 g mol− 1; one (M2005), two (D2000), and three (T3000) primary amino groups end-capping on the polyether backbone; and propylene oxide (PO) and ethylene oxide (EO) functionality were explored as additives for application in MAPbI 3 perovskite solar cells (PSCs). The results indicated that the embedding of Jeffamine additives effectively passivates the defects in the grain boundaries of perovskite through the coordination bonding between the nitrogen atom and the uncoordinated lead ion of perovskite. We fabricated p–i–n PSC devices with the structure of glass/indium tin oxide (ITO)/NiO x/CH 3 NH 3 PbI 3 (with and without Jeffamine)/PC 61 BM/BCP/Ag. We observed the interaction between the Jeffamine and perovskites. This interaction led to increased lifetimes of the carriers of perovskite, which enabled …..Read More

Chun‐Kai Wang, Bing‐Huang Jiang, Jong‐Hong Lu, Ming‐Tsang Cheng, Ru‐Jong Jeng, Yu‐Wei Lu, Chih‐Ping Chen, Ken‐Tsung Wong

The Cover Feature shows a near‐infrared (NIR) absorption molecule acceptor for organic photovoltaics. The newly synthesized material PTTtID‐Cl exhibits strong absorption in the NIR region (700–881 nm). The constructed organic photovoltaic device based on a polymer donor (PM7) and two non‐fullerene acceptors (IT‐4F and PTTtID‐Cl) shows a power conversion efficiency up to 12.0 %. In addition, employing the Ag/ITO/Ag microcavity structure, semitransparent colorful devices were obtained. More information can be found in the Full Paper by C.‐K. Wang, B.‐H. Jiang, et al. on page 903 in Issue 5, 2020 (DOI: 10.1002/cssc.201903087)...Read More

Chun‐Kai Wang, Bing‐Huang Jiang, Jong‐Hong Lu, Ming‐Tsang Cheng, Ru‐Jong Jeng, Yu‐Wei Lu, Chih‐Ping Chen, Ken‐Tsung Wong

An acceptor–donor–acceptor (A–D–A)‐type non‐fullerene acceptor (NFA), PTTtID‐Cl, featuring thieno[3,2‐b]thieno[2′′′,3′′′:4′′,5′′]‐pyrrolo[2′′,3′′:4′,5′]thieno[2′,3′:4,5]thieno‐[2,3‐d]pyrrole (DTPTt) as the electron‐rich core and 2‐(5,6‐dichloro‐3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile (ID‐Cl) as the peripheral electron‐deficient terminal group was synthesized and characterized. PTTtID‐Cl exhibited strong absorption in the range of 700–850 nm in CHCl3 and redshifted absorption centered at 881 nm in a thin film. The near infrared (NIR)‐absorption of PTTtID‐Cl was combined with a low‐bandgap polymer donor (PTB7‐Th) to achieve binary and semitransparent organic photovoltaics (OPVs) with a power conversion efficiency (PCE) of 8.9 % and 7.7 % (with an average visible transmittance (AVT) of 16.7 %), respectively. A ternary device with a ratio of PM7/PTTtID‐Cl/IT ..Read More

Yan-Ru Lin, Yung-Sheng Liao, Hsiang-Tse Hsiao, Chih-Ping Chen

In this study, we applied two-step annealing to nickel oxide (NiOx) films that we then used in perovskite solar cells (PSCs). The optimized annealing process resulted in a change in the structure and chemical composition of the NiOx, leading to a change in the work function and improved conductivity for NiOx-coated ITO substrates. X-ray photoelectron spectroscopy suggested that a change in the Ni2+/Ni3+ ratio of NiO (Ni 2p at 854.0 eV) and the presence of Ni3+ species induced by vacancies in Ni2O3 (Ni 2p at 855.6 eV) and NiOOH (Ni 2p at 856.7 eV) were responsible for the enhanced conductivity of the two-step-annealed NiOx films. The modified NiOx served as an efficient hole transporting layer, enhancing the PL quenching behavior at the perovskite–NiOx interface. Time-resolved photoluminescence measurements provided evidence for efficient carrier extraction. These improvements led to increases in …..Read More

Yung‐Chung Chen, Yan‐Heng Li, Chung‐Lin Chung, Hsiang‐Lin Hsu, Chih‐Ping Chen

This paper discusses a series of triphenylamine dibenzofulvene–based hole transporting materials (HTMs) featuring different numbers of MeO groups (none for YC‐1, four for YC‐2, and six for YC‐3) and their use in p‐i‐n perovskite solar cells (PSCs). We investigated the optoelectronic properties of these HTMs and found that the PSC devices incorporating YC‐1 as HTMs exhibited power conversion efficiencies (PCEs) of 15.78 ± 0.61%, which outperformed the corresponding PEDOT:PSS‐based device (12.80 ± 1.31%) under similar testing conditions. We then employed YC‐1 for the interfacial modified layer of a NiOx‐derived PSC having the structure ITO/NiOx/YC‐1/CH3NH3PbI3/PC61BM/bathocuproine/Ag. The presence of YC‐1 promoted the growth of micrometer‐sized grains of perovskite and induced a lower content of grain boundary defects, both of which improved the carrier extraction. Thereby, compared …..Read More

Shih‐Han Huang, Cheng‐Kang Guan, Pei‐Huan Lee, Hung‐Che Huang, Chia‐Feng Li, Yu‐Ching Huang, Wei‐Fang Su

Currently, high‐efficiency perovskite solar cells are mainly fabricated by the spin‐coating process, which limits the possibility of commercial mass‐production of perovskite solar cells. In this work, the slot‐die coating process is combined with near‐infrared irradiation heating to quickly manufacture perovskite solar cells in air. The composition of the perovskite precursor solution is tuned by adding n‐butanol, with its low boiling point and low surface tension, to increase the near‐infrared energy absorption, facilitate the evaporation of the solvent system and film formation, and accelerate the crystallization of perovskite. High‐quality uniform perovskite film can be prepared within 18 s. Moreover, the all slot‐die coating process is demonstrated to prepare over an area of 12 cm × 12 cm, four layers of uniform film overlay on top of each other for the devices except electrode in ambient air. A power conversion efficiency of …..Read More

Shih-Han Huang, Kuo-Yu Tian, Hung-Che Huang, Chia-Feng Li, Wei-Cheng Chu, Kun-Mu Lee, Yu-Ching Huang, Wei-Fang Su

Low-cost and solution-processed perovskite solar cells have shown great potential in scaling-up for mass production. In comparison with the spin-coating process of fabricating devices with small area, the blade coating process is a facile technique of preparing uniform films with large area. High efficiency perovskite solar cells has been reported using blade coating but they were fabricated using the toxic solvent of N,N-dimethylformide (DMF) in nitrogen. In this work, we present highly efficient blade-coated perovskite solar cells prepared using a green solvent mixture of gamma-butyrolactone (GBL) and dimethyl sulfoxide (DMSO) in ambient environment. By carefully controlling the interface, morphology and crystalline of perovskite film through composition variations and additive, a high power conversion efficiency of 17.02% is achieved in air with 42.4% reduction of standard deviation in performance. The findings …..Read More

Pei-Huan Lee, Bo-Ting Li, Chia-Feng Lee, Zhi-Hao Huang, Yu-Ching Huang, Wei-Fang Su

Lead halide perovskite solar cells (PVSCs) have potential toward commercialization because of their high efficiency and low cost. The hole transport layer (HTL) of p-i-n perovskite solar cell is usually made of NiOX. However, the NiOX needs to be processed at 300 °C for 15 min for good hole transport property. This long heating time prohibits the development of continuous commercial process. Thus, a rapid heating process for the NiOX film deposition is critical to realize the commercialization of PVSCs in the future. In this study, we develop a facile method to obtain high quality NiOX films annealed by NIR in a short time of 50 s. A short-wave NIR lamp at 2500 K was used to systematically investigate the effect of NIR intensity on the film quality of sol-gel NiOX. The PVSCs fabricated from NIR-annealed NiOX (NIR-NiOX) film show a comparable power conversion efficiency (PCE) to those fabricated from traditional hot …..Read More

Ming-Chung Wu, Chih-Kunag Kao, Tz-Feng Lin, Shun-Hsiang Chan, Shih-Hsuan Chen, Chi-Hung Lin, Yu-Ching Huang, Ziming Zhou, Kai Wang, Chao-Sung Lai

Volatile organic compounds (VOCs) are potentially dangerous to the environment and human health. The developed sensing template in this study was prepared by a one-step process on a glass substrate using the electrospinning technique. The sensing material made of the uniaxial aligned CdSe-CdS/Ag/PMMA composite scaffold consists of CdSe-CdS core-shell quantum rods, silver nanoparticles (Ag NPs), and poly(methyl methacrylate) (PMMA) nanofibers. Increasing the specific surface area is beneficial for VOCs harvesting; therefore, the uniaxial aligned CdSe-CdS/Ag/PMMA composite scaffold was slightly treated with UV-ozone etching, and thus efficiently enhancing the extinction changes of VOCs. Also, a high VOC detection capability was demonstrated by the polarization response and Ag surface plasmon resonance of the nanocomposite. A series of typical VOCs and alcoholic VOCs were used for the …..Read More

Chuang-Yi Liao, Yao Chen, Chun-Chieh Lee, Gang Wang, Nai-Wei Teng, Chia-Hao Lee, Wei-Long Li, Yu-Kuang Chen, Chia-Hua Li, Hsiuan-Lin Ho, Phoebe Huei-Shuan Tan, Binghao Wang, Yu-Chin Huang, Ryan M Young, Michael R Wasielewski, Tobin J Marks, Yi-Ming Chang, Antonio Facchetti

A series of readily accessible and scalable benzo[1,2-b:4,5-b′]dithiophene (BDT)-2,5-dithienyl-thieno[3,4-c]pyrrole-4,6-dione (TPD-T2)-based donor polymers are utilized in organic photovoltaic (OPV) cells blended with the non-fullerene acceptor IT-4F. All polymers readily dissolve in chlorine-free solvents such as xylene, and the corresponding photoactive blend films can be processed in ambient from this solvent to fabricate cells with power conversion efficiencies (PCEs) >12%–14%. Furthermore, the blend processing and OPV metrics are remarkably insensitive to the processing methodology (spin coating versus blade coating), processing solvent, polymer molecular mass and dispersity index, and the results were rationalized by UV-vis, PL, fsTA, AFM, TEM, GIWAXS, and SCLC measurements. These properties enable the first OPV modules, processed in ambient from a benign solvent, with a certified PCE of …..Read More

Miaosheng Wang, Ya-Ze Li, Hung-Cheng Chen, Che-Wei Liu, Yi-Sheng Chen, Yuan-Chih Lo, Cheng-Si Tsao, Yu-Ching Huang, Shun-Wei Liu, Ken-Tsung Wong, Bin Hu

This paper demonstrates high-efficiency organic near-infrared (NIR) photodetection activity by increasing the symmetry of photoinduced charge density based on planar cyclic donor–acceptor structures. The record-high photosensing capability (gain: 3 × 105 and EQE: 43% at 3 V) is realized under NIR 780 nm illumination upon using the single-component active layer chloroaluminum phthalocyanine (ClAlPc) with planar cyclic intramolecular donor–acceptor structures to create four-fold symmetry of photoinduced charge density. Our in situ measurement using bias-dependent magneto-photocurrent reveals that increasing the symmetry of photoinduced charge density through planar cyclic intramolecular donor–acceptor structures can significantly decrease the electron–hole binding energies, allowing the direct generation of free photogenerated carriers without any heterojunction structures. Particularly, with the four …..Read More

Hoang Chinh Nguyen, Dat Phu Vuong, Ngoc Thanh Tam Nguyen, Nguyen Phuong Nguyen, Chia-Hung Su, Fu-Ming Wang, Horng-Yi Juan

Sacha inchi seeds are a potential source of natural oil rich in essential polyunsaturated fatty acids and have various nutraceutical and health benefits. This study developed an aqueous enzymatic extraction process for eco-friendly extracting sacha inchi seed oil. The activities of different enzymes (proteases and cellulase) in the extraction process were evaluated. Among the tested enzymes, papain exhibited the highest extraction activity. The papain-assisted extraction was subsequently optimized through response surface methodology to yield maximum oil level. A maximum oil yield of 28.45% was obtained under the following extraction conditions: enzyme loading, 4.46%; water-to-sample ratio, 4.45 mL/g; extraction time, 4.95 h; and temperature, 38.9 °C. Under optimal extraction conditions, papain could be repeatedly used for extraction. This study indicates that papain is a potential protease and that aqueous …..Read More

Dinh Duc Nguyen, Ali Habibi, Azam Ghadami, Vahid Pirouzfar, Chia-Hung Su

The transesterification process with potassium hydroxide (KOH) catalyst and the methanol supercritical process were evaluated by Aspen HYSYS software. Castor oil and methanol were used as feed and alcohol. In order to accomplish verification, the simulation results were compared to a laboratory research. For economic analysis, these results were transferred to Aspen Economic Analyzer software. Piping and process equipment cost were calculated for the two processes. Additionally, direct and indirect costs of these processes were estimated...Read More

Berhanemeskel Atsbeha Kahsay, Fu-Ming Wang, Alem Gebrelibanos Hailu, Chia-Hung Su

Low-molecular-weight carbonyl-containing compounds are considered beneficial energy storage materials in alkali metal-ion/alkaline earth metal-ion secondary batteries owing to the ease of their synthesis, low cost, rapid kinetics, and high theoretical energy density. This study aims to prepare a novel carbonyl compound containing a maleamic acid (MA) backbone as a material with carbon black to a new MA anode electrode for a lithium-ion battery. MA was subjected to attenuated total reflection-Fourier-transform infrared spectroscopy, and its morphology was assessed through scanning electron microscopy, followed by differential scanning calorimetry to determine its thermal stability. Thereafter, the electrochemical properties of MA were investigated in coin cells (2032-type) containing Li metal as a reference electrode. The MA anode electrode delivered a high reversible capacity of about 685 mAh g− 1 in the first cycle and a higher rate capability than that of the pristine carbon black electrode. Energy bandgap analysis, electrochemical impedance, and X-ray photoelectron spectroscopy revealed that MA significantly reduces cell impedance by reforming its chemical structure into new nitrogen-based highly ionic diffusion compounds. This combination of a new MA anode electrode with MA and carbon black can increase the performance of the lithium-ion battery, and MA majorly outweighs transitional carbon black. View Full-Text..Read More

Tuyet Nhung Tran, Dai-Hung Ngo, Quoc Tuan Tran, Hoang Chinh Nguyen, Chia-Hung Su, Dai-Nghiep Ngo

Astaxanthin is a valuable carotenoid, which has been approved as a food coloring by the US Food and Drug Administration and is considered as a food dye by the European Union (European Commission). This work aimed to attain Rhodosporidium toruloides mutants for enhanced astaxanthin accumulation using ultraviolet (UV) and gamma irradiation mutagenesis. Gamma irradiation was shown to be more efficient than UV for producing astaxanthin-overproducer. Among the screened mutants, G17, a gamma-induced mutant, exhibited the highest astaxanthin production, which was significantly higher than that of the wild strain. Response surface methodology was then applied to optimize the medium compositions for maximizing astaxanthin production by the mutant G17. The optimal medium compositions for the cultivation of G17 were determined as a peptone concentration of 19.75 g/L, malt extract concentration of 13.56 g/L, and glucose concentration of 19.92 g/L, with the maximum astaxanthin yield of 3021.34 µg/L±16.49 µg/L. This study suggests that the R. toruloides mutant (G17) is a potential candidate for astaxanthin production. View Full-Text..Read More

Hoang Chinh Nguyen, Hwai Chyuan Ong, Thi Thanh Truc Pham, Thi Kim Khue Dinh, Chia‐Hung Su

This study developed a new catalyst‐free process for producing ethyl levulinate, a biofuel additive. Noncatalytic levulinic acid esterification with ethanol using microwave irradiation (MW) was compared with that using traditional heating (TH) under different reaction conditions. The results demonstrated that the esterification process using MW was more effective than that using TH. A reaction conversion of 90.38% was obtained for the esterification using MW at 473 K and reaction time of 3 hours. Moreover, this study established a model for depicting the kinetics of levulinic acid esterification using MW and TH. A good fit to the data (R2 of >.9999) was achieved, indicating the validity of the developed model. The rate constants and pre‐exponential factor obtained for the esterification using MW were greater than those obtained using TH. Consequently, the microwave‐assisted noncatalytic synthesis is a green and …..Read More

Hoang Chinh Nguyen, Kuan-Chieh Huang, Chia-Hung Su

Phytosterol esters are compounds with health benefits and widespread industrial applications. In this work, the noncatalytic esterification of phytosterols and oleic acid was efficiently conducted using microwave irradiation for producing phytosterol esters. The influences of the reaction parameters on the phytosterol conversion were examined. The reaction conversion increased with increasing oleic acid:phytosterols molar ratio, microwave power, temperature, and reaction time. The phytosterol conversion of 95.42% was achieved at a temperature of 453 K, microwave power of 200 W, oleic acid:phytosterols molar ratio of 5:1, and reaction time of 50 min. Fourier transform infrared spectroscopy was employed to identify the molecular structure of the synthesized phytosterol esters. A second-order kinetic model was successfully developed for describing the esterification reaction. This study suggests that noncatalytic …..Read More

Chia‐Hung Su, Thi Thanh Truc Pham, Hsien‐Hao Cheng

Introduction Rosmarinic acid is a bioactive compound with various pharmaceutical effects and applications. Objective This work developed a new approach for aqueous enzymatic extraction of rosmarinic acid from the leaves of Salvia officinalis. Methods Different enzymes (proteases and cellulase) were evaluated for their extraction activity. Response surface methodology (RSM) was subsequently employed to optimise the extraction conditions. Thin layer chromatography was also used to identify rosmarinic acid in the extract of S. officinalis. Results Among the tested enzymes, a Cellulase A and Protamex mixture (1:1, w/w) exhibited maximum effectiveness in the extraction. Through the use of RSM, the maximum rosmarinic acid content of 28.23 ± 0.41 mg/g was obtained with enzyme loading of 4.49%, water‐to‐sample ratio of 25.76 mL/g, temperature of 54.3°C, and extraction time of 2 h. Conclusion This study …..Read More

Hoang Chinh Nguyen, Fu-Ming Wang, Kim Khue Dinh, Thanh Truc Pham, Horng-Yi Juan, Nguyen Phuong Nguyen, Hwai Chyuan Ong, Chia-Hung Su

This study developed a microwave-mediated noncatalytic esterification of oleic acid for producing ethyl biodiesel. The microwave irradiation process outperformed conventional heating methods for the reaction. A highest reaction conversion, 97.62%, was achieved by performing esterification with microwave irradiation at a microwave power of 150 W, 2: 1 ethanol: oleic acid molar ratio, reaction time of 6 h, and temperature of 473 K. A second-order reaction model (R 2 of up to 0.997) was established to describe esterification. The reaction rate constants were promoted with increasing microwave power and temperature. A strong linear relation of microwave power to pre-exponential factors was also established, and microwave power greatly influenced the reaction due to nonthermal effects. This study suggested that microwave-assisted noncatalytic esterification is an efficient approach for biodiesel synthesis. View Full-Text..Read More

Hoang Chinh Nguyen, Hao-Yeh Lee, Chia-Hung Su, Wei-Jhih Shih, Chien-Chung Chien

This study developed a new method that involved autocatalytic hydrolysis of soybean oil using microwave irradiation for fatty acid production. To enhance the conversion yield, a surfactant and fatty acid were added to the reaction mixture. The oil hydrolysis using microwave irradiation had 96.6 % conversion yield within a reaction time of 4 h at 195 °C. Furthermore, this study established a model for describing the kinetics of oil hydrolysis performed using traditional heating and microwave irradiation under different reaction conditions. The model exhibited a good fit to the data (R2 of 0.934 to 0.995), demonstrating the reliability of the developed model. The rate constants and pre-exponential factor observed for the oil hydrolysis process using microwave irradiation were higher than those observed for the oil hydrolysis process using traditional heating, indicating that performing oil hydrolysis by using microwave …..Read More

Hoang Chinh Nguyen, My Linh Nguyen, Shih-Hsiang Liang, Chia-Hung Su, Fu-Ming Wang

DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), a polarity switchable solvent, has been recognized as a green solvent for oil extraction and as a promising catalyst for transesterification. This paper proposes a novel method that combines the dual functions of DBU in direct transesterification. The effects of reaction parameters on the direct transesterification of black soldier fly larvae with methanol when using DBU as both a catalyst and solvent were investigated, and a 96.2% biodiesel yield was achieved at a DBU-to-biomass ratio of 16:1 (mL/g), methanol-to-biomass ratio of 8:1 (mL/g), temperature of 110 °C, and reaction time of 60 min. Remarkably, because of its polarity reversibility, DBU was easily separated and recovered from the reaction solution through phase separation and could be repeatedly used up to 10 times without a considerable loss of catalytic activity. DBU-catalyzed direct transesterification is a green …..Read More

Hoang Chinh Nguyen, My Linh Nguyen, Fu-Ming Wang, Horng-Yi Juan, Chia-Hung Su

Spent coffee grounds (SCGs) are a promising material for sustainable preparation of biodiesel. This study proposed a new approach for biodiesel synthesis from wet SCGs using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as both a green solvent and catalyst. The optimal reaction conditions were determined as a methanol amount of 6.25 mL/g of wet SCGs, DBU amount of 14.46 mL/g of wet SCGs, temperature of 60.2 °C, and reaction time of 28.65 min through response surface methodology. Under these conditions, the maximum biodiesel yield was 97.18%. Notably, DBU polarity could be regulated reversibly, facilitating its reusability and a simple process for product separation. Under optimal conditions, DBU could be potentially reused for at least 10 cycles to yield high amounts of biodiesel. This study suggests that the switchable solvent-assisted direct transesterification of wet SCGs is a potential, efficient …..Read More

Cheng-Shane Chu, Cheng-Yi Lin

This paper presented a new ratiometic optical sensor for sensing of urea concentrations based on CdSe/ZnS QDs and Rhodamine 110 (Rh110) doped in poly (isobutyl methacrylate) coated on the surface of glass...Read More

Publications 2019

Saurabh Tiwari, Gyanendra Rathore, N Patra, AK Yadav, Dibyendu Bhattacharya, SN Jha, CM Tseng, SW Liu, Sajal Biring, Somaditya Sen

Local and long-range structural properties, of sol-gel synthesized, Ce1-xNixO2 (0 ≤ x ≤ 0.1) nanopowders have been investigated. Substitution of Ce4+ by comparably smaller Ni2+/Ni3+ ions leads to decrement in lattice parameters. UV–visible spectra reveal decrease of bandgap with increase of disorder upon increasing Ni substitution. The photoluminescence (PL) spectra reveal five major peaks attributed to various defect states. Ni substitution results in the creation of oxygen vacancies (VO) which further leads to conversion of considerable amount of Ce4+ ions to larger size Ce3+. These changes notably, modify the structure of the host lattice. The defects created along with the structural modifications bring, changes in the PL emission. The disorder in the lattice results in increase of non-radiative decay which reduces the PL emission. An increasing VO and Ce3+ concentration at the surface acts as … ...Read More

Chih-Chien Lee, Sajal Biring, Shiang-Jen Ren, Ya-Ze Li, Meng-Zhen Li, Nurul Ridho Al Amin, Shun-Wei Liu

The work function at the surface of 4,4′Cyclohexylidenebis[N,N-bis(4-methylphenyl) benzenamine (TAPC) layer could be increased by doping MoO3 having high ionization energy. Therefore, in this work, we attempted to dope MoO3 into electron-blocking layer material of TAPC to improve the device performance of organic photodetector (OPD), which effectively suppressed dark current density and increased external quantum efficiency (EQE). When a 5% MoO3 dopant was used, the optimal OPD under reverse-biased of 3 V showed a dark current density of 1.11 nA/cm2, the EQE of 41.8% under a wavelength of 360 nm, and the detectivity of the specific wavelength surpassed 1012 Jones. In this study, we found that the decrease in the dark current density was responsible to the lower energy level of lowest unoccupied molecular orbital of TAPC and slower electron transporting capacity, which enabled the …..Read More

Saurabh Tiwari, Nasima Khatun, N Patra, AK Yadav, Dibyendu Bhattacharya, SN Jha, CM Tseng, SW Liu, Sajal Biring, Somaditya Sen

Single phase Co/Ni substituted CeO2 nanoparticles reveal the importance of oxygen vacancies on the electronic properties of the materials. The effect of Co/Ni substitution on the structural, optical, and photoluminescence properties of CeO2 have been studied systematically. Lattice shrinks and hence strain increase owing to incorporation of Co/Ni in CeO2. Optical absorption analysis shows a red shift in band-gap with Co/Ni substitution. Photoluminescence studies reveals increase in defect concentration which causes quenching of PL emission. Vibration modes at ~460 cm−1 in Raman spectra indicates incorporation of Co/Ni in CeO2 lattice whereas a broad peak appearing at ~ 540–640 cm−1 with substitution depicts the defects related to the increase in oxygen vacancy. X-ray absorption (XAS) studies show that Co/Ni substitution maintains local structure while Ce4+ → Ce3+ concentration increases to …..Read More

Nitesh K Chourasia, Anand Sharma, Vishwas Acharya, Nila Pal, Sajal Biring, Bhola N Pal

Low band gap ion conducting Li2ZnO2 thin film has been synthesized by low cost solution processed technique and has been employed to fabricate low operating voltage metal oxide thin film transistor (TFT) with high device performance. Li2ZnO2 is a known ion conducting oxide material, generally used as solid state electrolyte in different applications including fuel cell and Li ion battery. Instead of having low band gap, Li2ZnO2 thin film shows very insulating behavior and low leakage current. Additionally, it shows high dielectric constant (κ) that originated from the conducting nature of its Li+ ion, serve as a gate dielectric for low operating voltage metal oxide TFT. In addition to this dielectric, tin oxide (SnO2) semiconductor channel has also been deposited in solution processed technique in the bottom gate top contact TFT structure. Such kind of TFT device requires only 2.0 V or less drain voltage with the gate … ..Read More

Mohd Nasir, Sunil Kumar, Nirmalendu Patra, Dibyendu Bhattacharya, Shambhu Nath Jha, Dharma R Basaula, Subhash Bhatt, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Homogeneous solid solutions of sol–gel-prepared R2NiMnO6 (R = La, Pr, Nd, Sm, Gd, Tb, Dy, Y, and Ho) double perovskites crystallize in a B-site-ordered monoclinic structure (P21/n space group). Monoclinic distortion enhances with decreasing R3+ ionic radii (rR3+). The magnetic ordering temperature (TC) decreases from 270 K for La2NiMnO6 to 80 K for Ho2NiMnO6 as rR3+ decreases from 1.16 Å (La3+) to 1.02 Å (Ho3+)...Read More

Gaurav Bajpai, Igamcha Moirangthem, Shuvam Sarkar, Sudipta Roy Barman, CP Vinod, Shubhra Bajpai, Sk Riyajuddin, Kaushik Ghosh, Dharma R Basaula, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

When Fe is doped in ZnO, a situation of charge imbalance is created due to the higher charge of Fe3+. A charge balance may be obtained by co-doping Li+0.5Fe3+0.5 combinations. A solid solution of Zn1-x(Fe0.5Li0.5)xO (0 ≤ x ≤0.03125) is synthesized with this viewpoint. The crystallites belong to a wurtzite P63mc space group, with lattice parameters a, b and c increasing nominally for x = 0.0156 and thereafter remaining invariant. The size varies in the range ~ 60–142 nm. Interstitials of Li and Zn ions are formed. Along with Fe3+ substitution these defects are reasons for O interstitials. ..Read More

Mahmud Khan Basaula, Shun-Wei Liu, Sajal Biring, Somaditya Sen, Sudipta Roy Barman, CP Vinod, Shubhra Bajpai, Sk Riyajuddin, Kaushik Ghosh, Dharma R Basaula, Mahmud Khan

When Fe is doped in ZnO, a situation of charge imbalance is created due to the higher charge of Fe 3+. A charge balance may be obtained by co-doping Li+ 0.5Fe 3+ 0.5 combinations. A solid solution of Zn1-x (Fe0. 5Li0. 5) xO (0≤ x≤ 0.03125) is synthesized with this viewpoint. The crystallites belong to a wurtzite P63mc space group, with lattice parameters a, b and c increasing nominally for x= 0.0156 and thereafter remaining invariant. The size varies in the range~ 60-142 nm. Interstitials of Li and Zn ions are formed. Along with Fe 3+ substitution these defects are reasons for O interstitials. These oxygen interstitials increase the red emission while reduction of oxygen vacancies reduces the green emission...Read More

Anita Verma, Arun Kumar Yadav, Sunil Kumar, Velaga Srihari, Ravindra Jangir, Himanshu K Poswal, Shun-Wei Liu, Sajal Biring, Somaditya Sen

The effects of electric field and temperature on structural, dielectric, and ferroelectric properties of (1 – x)(Na0.50Bi0.50TiO3)-xAgTaO3 (x = 0, 0.03, 0.05, and 0.10) ceramics prepared via the modified sol-gel method were investigated. Rietveld refinement of synchrotron radiation x-ray diffraction data (SRPXRD) confirmed the rhombohedral (R3c) phase in all the unpoled samples. After poling, the samples remained in the rhombohedral phase for x ≤ 0.03, whereas for x ≥ 0.05, it showed a mixed rhombohedral and tetragonal (P4bm) phase. ..Read More

Chia-Hsun Chen, Hao-Chun Ting, Ya-Ze Li, Yuan-Chih Lo, Pin-Hao Sher, Juen-Kai Wang, Tien-Lung Chiu, Chi-Feng Lin, I-Sheng Hsu, Jiun-Haw Lee, Shun-Wei Liu, Ken-Tsung Wong

Four new donor-acceptor-acceptor (D-A-A) type molecules (DTCPB, DTCTB, DTCPBO, DTCTBO), where benzothiadiazole (BT) or benzoxadiazole (BO) serves as the central A bridging triarylamine (D) and cyano group (terminal A), have been synthesized and characterized. The intramolecular charge transfer character renders these molecules with strong visible light absorption and form anti-parallel dimeric crystal packing with evident π-π intermolecular interactions. ..Read More

Anand Sharma, Nitesh K Chourasia, Vishwas Acharya, Nila Pal, Sajal Biring, Shun-Wei Liu, Bhola N Pal

Low surface-roughness and high-capacitance ion-conducting LiAlO2 gate dielectric thin film has been fabricated by sol–gel technique to develop ultra-low voltage (≤ 1.0 V) indium-zinc-oxide thin film transistor (TFT). This LiAlO2 dielectric shows α-LiAlO2 and γ-LiAlO2 phases those have been fabricated at two different temperatures. For both phases, mobile Li-ion is responsible to achieve a high dielectric constant (κ) of the material that helps to reduce the operating voltage of TFT. Additionally, lower surface roughness of LiAlO2 thin film.....Read More

Miaosheng Wang, Yi‐Hsuan Huang, Kai‐Siang Lin, Tzu‐Hung Yeh, Jiashun Duan, Tzu‐Yu Ko, Shun‐Wei Liu, Ken‐Tsung Wong, Bin Hu

Experimental studies to reveal the cooperative relationship between spin, energy, and polarization through intermolecular charge‐transfer dipoles to harvest nonradiative triplets into radiative singlets in exciplex light‐emitting diodes are reported. Magneto‐photoluminescence studies reveal that the triplet‐to‐singlet conversion in exciplexes involves an artificially generated spin‐orbital coupling (SOC). The photoinduced electron parametric resonance measurements indicate that the intermolecular charge‐transfer occurs with forming electric dipoles (D+•→ A−•),.....Read More

Addanki Venkateswararao, Johnny KW Ho, Shu Kong So, Shun-Wei Liu, Ken-Tsung Wong

Indoor photovoltaics (IPVs), which convert the indoor light energy into direct electricity, have attracted research attention due to their potential use as an excellent amicable solution of sustainable power source to drive low-power-needed sensors for the internet of things (IoT) applications. Our daily life adopts various indoor light sources, such as indirect sunlight, incandescent lamps, halogen lamps, fluorescent lamps, and LED bulbs, that typically deliver lower light intensity (200–1000 lux) as compared to that of sun light (∼100,000 lx). In this review, we firstly......Read More

Gaurav Bajpai, Mayank Ostawal, Igamcha Moirangthem, Shubhra Bajpai, Dharma R Basaula, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Fe incorporation in ZnO lattice draws more oxygen which reduces oxygen vacancies. The smaller size and larger charge of the Fe3+ ion helps to reduce strain initially but with increased substitution generates more strain due to excess oxygen and structural deformation. The mismatch of ionic radii may be addressed by co-substituting with a larger element but with lesser charge. Oxygen defects play a vital role in magnetization and UV-sensing properties of pure ZnO. Oxygen vacancy mediated ferromagnetic exchange interaction should reduce......Read More

Purushotham Thatiboyana, Sajal Biring, Chih-Chien Lee, Shun-Wei Liu

We introduce a high-efficiency small-molecule organic photovoltaic (OPV) device which can emit different color with different thickness of the organic layer. In this OPV device, we can change the color output by simply tuning the thickness organic layer which forms microcavity cathode between layers of silver. Our OPV exhibited a highest power conversion efficiency of 5.48%, with an open circuit voltage of 0.89 V, and short-circuit current density of 9.17 mA/cm 2 ...Read More

Yuan-Chih Lo, Tzu-Hung Yeh, Chun-Kai Wang, Bo-Ji Peng, Jing-Lin Hsieh, Chih-Chien Lee, Shun-Wei Liu, Ken-Tsung Wong

Three DAD-configured molecules DTPBT, DTPNT, and DTPNBT with high quantum yield of orange red (628 nm), red (659 nm), and deep-red/NIR (710 nm) fluorescence, respectively, were developed as emitting dopants in an exciplex-forming cohost (TCTA: 3P-T2T) for high-efficiency fluorescence-based organic light-emitting diodes (OLEDs). The obtained physical properties together with theoretical calculations analyzed from these new molecules establish a clear structure-property relationship, in which the feature of central acceptor 2, 1, 3.....Read More

Sajal Biring, Yun-Ming Sung, Thanh Phuc Nguyen, Ya-Ze Li, Chih-Chien Lee, Alvin Hsien Yi Chan, Bholanath Pal, Somaditya Sen, Shun-Wei Liu, Ken-Tsong Wong

Open circuit voltage of a photovoltaic system, in general, is constrained by the Schottky barrier (SB) heights formed at the electrodes. Here, the SB heights which are inhomogeneous in nature at the anode-semiconductor junction of a donor-acceptor-acceptor molecule, 2-[(7-(4-[N,N-bis(4-methylphenyl)amino]phenyl)-2,1,3-benzothia-diazol-4-yl)methylene] propane-dinitrile (DTDCPB), mixed with C70 as a bulk heterojunction have been studied thoroughly by......Read More

Yuan-Chih Lo, Tzu-Hung Yeh, Chun-Kai Wang, Bo-Ji Peng, Jing-Lin Hsieh, Chih-Chien Lee, Shun-Wei Liu, Ken-Tsung Wong

hree D-A-D-configured molecules DTPBT, DTPNT and DTPNBT with high quantum yield of orange red (628 nm), red (659 nm) and NIR (710 nm) fluorescence, respectively, were developed as emitter doping in an exciplex-forming cohost (TCTA:3P-T2T) for high efficiency fluorescence-based OLEDs. The obtained physical properties together with theoretical calculations analyzed from these new molecules establish a clear structure-property relationship, in which the feature....Read More

Gaurav Bajpai, Sk Riyajuddin, Kaushik Ghosh, Shubhra Bajpai, Dharma R Basaula, Subhash Bhatt, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Structural, opto-electronics and magnetic hysteresis properties have been studied of sol–gel synthesized Zn (0.96875) Si (0.03125)-x Fe x O (0≤ x≤ 0.03125) nano-particles. The crystallites belong to a wurtzite P6 3 mc space group. The ratio of Si: Fe is varied in these materials. Si 4+ and Fe 3+ both attract oxygen to the lattice. The excess oxygen content reduces oxygen vacancies a....Read More

Saurabh Tiwari, Gyanendra Rathore, N Patra, AK Yadav, Dibyendu Bhattacharya, SN Jha, CM Tseng, SW Liu, Sajal Biring, Somaditya Sen

Local and long-range structural properties, of sol-gel synthesized, Ce1-xNixO2 (0 ≤ x ≤ 0.1) nanopowders have been investigated. Substitution of Ce4+ by comparably smaller Ni2+/Ni3+ ions leads to decrement in lattice parameters. UV–visible spectra reveal decrease of bandgap with increase of disorder upon increasing Ni substitution. The photoluminescence (PL) spectra reveal five major peaks attributed to various defect states. Ni substitution results in the creation of oxygen vacancies (VO) which further....Read More

Gaurav Bajpai, Igamcha Moirangthem, Shuvam Sarkar, Sudipta Roy Barman, CP Vinod, Shubhra Bajpai, Sk Riyajuddin, Kaushik Ghosh, Dharma R Basaula, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

When Fe is doped in ZnO, a situation of charge imbalance is created due to the higher charge of Fe3+. A charge balance may be obtained by co-doping Li+0.5Fe3+0.5 combinations. A solid solution of Zn1-x(Fe0.5Li0.5)xO (0 ≤ x ≤ 0.03125) is synthesized with this viewpoint. The crystallites belong to a wurtzite P63mc space group, with lattice parameters a, b and c increasing nominally for x = 0.0156 and thereafter remaining invariant. The size varies in the range ~ 60–142 nm.....Read More

Miaosheng Wang, Yi‐Hsuan Huang, Kai‐Siang Lin, Tzu‐Hung Yeh, Jiashun Duan, Tzu‐Yu Ko, Shun-Wei Liu*劉舜維, Ken‐Tsung Wong*, Bin Hu*

Experimental studies to reveal the cooperative relationship between spin, energy, and polarization through intermolecular charge‐transfer dipoles to harvest nonradiative triplets into radiative singlets in exciplex light‐emitting diodes are reported. Magneto …..Read More

Addanki Venkateswararao, Johnny KW Ho, Shu Kong So*, Shun-Wei Liu*劉舜維, Ken-Tsung Wong*

Indoor photovoltaics (IPVs), which convert the indoor light energy into direct electricity, have attracted research attention due to their potential use as an excellent amicable solution of sustainable power source to drive low-power-needed sensors for the internet of things (IoT) applications. Our daily life adopts various indoor light sources, such as indirect sunlight..Read More

Gaurav Bajpai, Mayank Ostawal, Igamcha Moirangthem, Shubhra Bajpai, Dharma R Basaula, Mahmud Khan, Shun-Wei Liu劉舜維, Sajal Biring畢少強, Somaditya Sen*

Fe incorporation in ZnO lattice draws more oxygen which reduces oxygen vacancies. The smaller size and larger charge of the Fe 3+ ion helps to reduce strain initially but with increased substitution generates more strain due to excess oxygen and structural deformation. The mismatch of ionic radii may be addressed by co-substituting with a larger element but with lesser charge. Oxygen defects play a vital role in magnetization and UV- sensing properties of pure ZnO. Oxygen vacancy mediated ferromagnetic exchange …..Read More

Yuan-Chih Lo, Tzu-Hung Yeh, Chun-Kai Wang, Bo-Ji Peng, Jing-Lin Hsieh, Chih-Chien Lee, Shun-Wei Liu*劉舜維, Ken-Tsung Wong

Three DAD-configured molecules DTPBT, DTPNT, and DTPNBT with high quantum yield of orange red (628 nm), red (659 nm), and deep-red/NIR (710 nm) fluorescence, respectively, were developed as emitting dopants in an exciplex-forming cohost (TCTA: 3P-T2T) for high- efficiency fluorescence-based organic light-emitting diodes (OLEDs). The obtained physical properties together with theoretical calculations analyzed from these new molecules establish a clear structure–property relationship, in which the feature of central acceptor 2, 1..Read More

Anita Verma, Arun Kumar Yadav, Nasima Khatun, Sunil Kumar, Ravindra Jangir, Velaga Srihari, V Raghavendra Reddy, Shun-Wei Liu劉舜維, Sajal Biring畢少強, Somaditya Sen*

The structural, dielectric and ferroelectric properties of lead-free (Na 0.5-x K x Bi 0.5-x La x) TiO 3 (0≤ x≤ 0.12) powders synthesized by modified sol-gel method was investigated. Rietveld refinement of synchrotron x-ray diffraction data confirms single phase rhombohedral crystal structure with R3c space group for all the compositions and anti-phase (aaa-) octahedral tilting angle decreased with increase in composition. Homogeneity and elemental proportions were confirmed by Energy dispersive x-ray spectrometry..Read More

Sajal Biring畢少強, Yun-Ming Sung, Thanh Phuc Nguyen, Ya-Ze Li, Chih-Chien Lee, Alvin Hsien Yi Chan, Bholanath Pal, Somaditya Sen, Shun-Wei Liu*劉舜維, Ken-Tsong Wong*

Open circuit voltage of a photovoltaic system, in general, is constrained by the Schottky barrier (SB) heights formed at the electrodes. Here, the SB heights which are inhomogeneous in nature at the anode-semiconductor junction of a donor-acceptor- acceptor molecule, 2-[(7-(4-[N, N-bis (4-methylphenyl) amino] phenyl)-2, 1, 3-benzothia- diazol-4-yl) methylene] propane-dinitrile (DTDCPB), mixed with C 70 as a bulk heterojunction have been studied thoroughly by inserting an insulating layer of MoO 3 with ..Read More

Gaurav Bajpai, Sk Riyajuddin, Kaushik Ghosh, Shubhra Bajpai, Dharma R Basaula, Subhash Bhatt, Mahmud Khan, Shun-Wei Liu*劉舜維, Sajal Biring*畢少強, Somaditya Sen

Structural, opto-electronics and magnetic hysteresis properties have been studied of sol–gel synthesized Zn (0.96875) Si (0.03125)-x Fe x O (0≤ x≤ 0.03125) nano-particles. The crystallites belong to a wurtzite P6 3 mc space group. The ratio of Si: Fe is varied in these materials. Si 4+ and Fe 3+ both attract oxygen to the lattice. The excess oxygen content reduces oxygen vacancies and further creates oxygen interstitials. However, there is a limit of oxygen intake as space is used up when a larger Fe 3+ ion substitutes a smaller Si 4+ ion …..Read More

Chia-Hsun Chen, Hao-Chun Ting, Ya-Ze Li, Yuan-Chih Lo, Pin-Hao Sher, Juen-Kai Wang, Tien-Lung Chiu, Chi-Feng Lin, I-Sheng Hsu, Jiun-Haw Lee*, Shun-Wei Liu*劉舜維, Ken-Tsung Wong*

Four new donor–acceptor–acceptor (D–A–A) type molecules (DTCPB, DTCTB, DTCPBO, and DTCTBO), wherein benzothiadiazole or benzoxadiazole serves as the central A bridging triarylamine (D) and cyano group (terminal A), have been synthesized and characterized. The intramolecular charge-transfer character renders these molecules with strong visible light absorption and forms antiparallel dimeric crystal packing with evident π– π intermolecular interactions. The characteristics of the vacuum-processed photovoltaic …..Read More

Mohd Nasir, Mahmud Khan, Subhash Bhatt, Anup Kumar Bera, Mohammad Furquan, Sunil Kumar, Sk Mohammad Yusuf, Nirmalendu Patra, Dibyendu Bhattacharya, Shambhu Nath Jha, Shun-Wei Liu劉舜維, Sajal Biring畢少強, Somaditya Sen*

Among multifunctional double perovskite oxides, La2NiMnO6 has recently drawn significant attention due to its importance both in terms of understanding of fundamental physics and potential for device applications. The relative alteration in Ni: Mn ratio strongly influences the structural and magnetic properties of La2NiMnO6. The cation ratio and degree of cation order significantly affect the magnetic coupling of the two B‐site cations in these compounds. In the present study, La2Ni1− xMn1+ xO6 (x=− 0.25, 0, 0.25) samples with different Ni: Mn …..Read More

Nasima Khatun, Saurabh Tiwari, Ruhul Amin, Chuan-Ming Tseng, Sajal Biring畢少強, Somaditya Sen*

A series of charge compensated Ga–V co-doped TiO 2 samples (Ti (1-x)(Ga 0.5 V 0.5) x O 2) have been synthesized by a modified sol-gel process. X-ray diffraction pattern shows that the anatase to rutile (A→ R) onset temperature (TO) shifts to a higher temperature, whereas the complete phase transformation temperature (TC) shifts to a low-temperature region as compared to pure TiO 2, due to Ga–V incorporation. Ga–V co-doping helps in the transformation of some smaller sized Ti 4+ to a relatively larger Ti 3+. In the anatase phase …..Read More

Nila Pal, Anand Sharma, Vishwas Acharya, Nitesh K Chourasia, Sajal Biring*畢少強, Bhola N Pal*,

A solution-processed high-performance subvolt (< 1 V) tin oxide (SnO2) thin film transistor (TFT) has been fabricated onto an ion-conducting Li–Al2O3 gate dielectric by utilizing a high- permittivity Mn2O3 gate interface. A comparative device characterization of two different TFTs with and without a Mn2O3 gate interface with an ionic dielectric ensures that n-type Mn2O3 induces an additional electron to the semiconductor/dielectric interface trap states. Consequently, the TFT with a Mn2O3 interface achieves a lower subthreshold swing (SS) by …..Read More

Prashant Kumar Mishra, Saniya Ayaz, Tulika Srivastava, Saurabh Tiwari, Ramraj Meena, Bungkiu Kissinquinker, Sajal Biring畢少強, Somaditya Sen*

Abstract Gallium (Ga 3+) doped ZnO with compositions Zn 1− x Ga x O (0≤ x≤ 0.0468) is prepared using the sol–gel method. ZnO Wurtzite structure having space group P6 3 mc is confirmed by using X-ray diffraction (XRD) measurement. The lesser ionic radii (0.62 Å) and higher charge (3+) of Gallium attracts more oxygen into the lattice and therefore a reduction in oxygen vacancies (VO) is observed. Photoluminescence (PL) study reveals that defects present in ZnO lattice decreases with Ga substitution. This is also reflected in Urbach energy …..Read More

Anita Verma, Arun Kumar Yadav, Sunil Kumar, Velaga Srihari, Ravindra Jangir, Himanshu K Poswal, Sajal Biring畢少強, Somaditya Sen*

Abstract Effect of substitution and external applied static electric field on the structural and dielectric properties for lead-free (1− x)(Na 0.50 Bi 0.50) TiO 3− x KSbO 3 (0≤ x≤ 0.06) polycrystalline ferroelectric ceramics, fabricated via a modified sol–gel method, were investigated. Structural analysis of synchrotron radiation X-ray diffraction data confirmed the rhombohedral R 3 c phase for all unpoled samples. After poling, the tetragonal P 4 bm phase appeared with the rhombohedral phase in all the substituted samples. In poled …..Read More

Mohd Nasir, Mahmud Khan, Sunil Kumar, Subhash Bhatt, Nirmalendu Patra, Dibyendu Bhattacharya, Shambhu Nath Jha, Sajal Biring畢少強, Somaditya Sen*

The ferromagnetic properties of the double perovskite La 2 NiMnO 6 are governed by the Ni 2+–O 2−–Mn 4+ superexchange interaction. The Ni 2+ and Mn 4+ valence states along with the antisite disorder strongly influence the magnetic interactions in the compound. Here, we report on the effect of high temperature annealing on the antisite disorder and related properties of La 2 NiMnO 6. X-ray absorption measurements reveal nominal changes in the local environment around B/B′ sites of all samples. However, saturation magnetization …..Read More

Anand Sharma, Nitesh K Chourasia, Nila Pal, Sajal Biring*畢少強, Bhola N Pal*

High-performance solution-processed one-volt metal-oxide thin-film transistor (TFT) has been fabricated onto highly p-doped silicon (p++-Si) substrate with sol–gel-derived ion- conducting gate dielectric by using electron-donating TiO2 gate interface. A comparative electrical characterization of two different TFTs with TiO2 and Al2O3 gate interface device reveals that n-type TiO2 works as an electron donor to the semiconductor/dielectric interface trap state. As a consequence, subthreshold swing (SS) of the TiO2 interface device reduces …..Read More

Anita Verma, Arun Kumar Yadav, Sunil Kumar, Velaga Srihari, Ravindra Jangir, Himanshu K Poswal, Sajal Biring畢少強, Somaditya Sen*

Detailed temperature-dependent structural, dielectric, piezo/ferroelectric, and energy storage properties were explored for the poled (Na 0.5-x K x Bi 0.5-x La x) TiO 3 (0≤ x≤ 0.12) ceramics fabricated via a modified sol-gel method. Structural analysis of synchrotron source powder XRD data revealed the rhombohedral (R3c) phase for poled x≤ 0.03 compositions. Whereas for x≥ 0.06 samples confirmed structural transition, a mix of rhombohedral and tetragonal (P4bm) phase exists at room temperature. As a function of …..Read More

Sheng-Chi Chen*, Sin-Yi Huang, Shikha Sakalley, Abhyuday Paliwal, Yin-Hung Chen, Ming-Han Liao, Hui Sun, Sajal Biring畢少強

In this work, we discuss the effects of working pressure on the microstructures, electrical, and optical properties of Cu 3 N films. The working pressures were varied from 5 mtorr to 23 mtorr while gas flow ratio of N 2 to Ar was maintained. When the working pressure increases, the Cu 3 N (111) peak intensity decreases as evident from the XRD analysis. The films' conductivity type also varies from n-type to p-type with increasing working pressure. When working pressure is 15 mtorr, the resistivity is 1.575 Ω cm and the sample conduction …..Read More

Arun Kumar Yadav, Anita Verma, Sunil Kumar, Sk Riyajuddin, Kaushik Ghosh, Sajal Biring畢少強, Somaditya Sen*

Abstract Polycrystalline PbTi (1− x)(Fe 0.50 V 0.50) x O 3 (0≤ x≤ 0.12) ceramics have been prepared using a modified sol–gel route via conventional sintering method. Rietveld refinement of all samples XRD data are carried out with tetragonal P 4 mm space group. Structural analysis is revealed to decrease the tetragonality (c/a) from 1.064 (for x= 0) to 1.039 (for x= 0.12) with increasing composition. An electronic structural study perceived that the hybridizations between Pb (6 s)–O (2 p)–Ti (3 d) orbitals are weakened with increasing …..Read More

Chih-Yi Liu*, Sajal Biring*畢少強,

A combination of focused ion beam lithography and a two-step anodization process has been used to fabricate an ideally long-range ordered nanoplatform containing short straight and long beer bottle-shaped nanochannels. The lithography is performed by direct ion irradiation to pattern an electro-polished aluminium sheet with a custom-designed array of nanoholes. The ion irradiation time for some selected nanoholes are longer than that for the others. All the nanoholes form an ideally ordered two-dimensional hexagonally close …..Read More

Vivek M Parimi, Abhirup Datta, Sajal Biring畢少強, Chia Hao Ku, Somaditya Sen

A novel Dielectric Resonator Antenna (DRA), simply made of Indium Tin Oxide (ITO) and Al or Ag coated glass slide of size 15mm x 15mm is studied in the frequency range1MHz- 12GHz. This study enables the applicability of such DRAs in the dual-band WLAN/WiMAX frequency range (2.4-5.85 GHz). The proposed antenna consists of a microstrip feedline that excites the ITO or metal coated DRAs. The three DRAs of ITO, Al and Ag coated glass slides of the same dimension have been compared with each other with reference to the original …..Read More

Nasima Khatun, Saurabh Tiwari, Ruhul Amin, Sajal Biring*畢少強

Vanadium substituted TiO2 samples are prepared by modified sol-gel process. X-ray diffraction (XRD) pattern and Raman spectra for all the samples reveal pure tetragonal phases of TiO2. Rutile percentage calculated from XRD pattern and Raman spectra follow a similar trend and signify that vanadium substitution promotes phase transformation from anatase to rutile. Due to aliovalent V substitution, donor levels are formed in the bandgap..Read More

Nitesh K Chourasia, Anand Sharma, Vishwas Acharya, Nila Pal, Sajal Biring*畢少強, Bhola N Pal

Low band gap ion conducting Li 2 ZnO 2 thin film has been synthesized by low cost solution processed technique and has been employed to fabricate low operating voltage metal oxide thin film transistor (TFT) with high device performance. Li 2 ZnO 2 is a known ion conducting oxide material, generally used as solid state electrolyte in different applications including fuel cell and Li ion battery. Instead of having low band gap, Li 2 ZnO 2 thin film shows very insulating behavior and low leakage current. Additionally, it shows high dielectric constant …..Read More

Himadri Sekhar Das, Prasanta Kumar Nandi, Sajal Biring畢少強, Rajesh Das

Organic-Inorganic Methylammonium lead Iodide (CH3NH3PbI3) based perovskite was prepared on mesoporous TiO2/ZnO: Ga (GZO) coated glass substrate with two step spin coating technique. Ga doped ZnO (ZnO: Ga) thin films have been deposited by RF- Magnetron sputtering at room temperature on glass substrate and show 4.3× 10− 4 Ω. cm electrical resistivity alongwith high optical transmittance (above 89%) and a haze factor of 52% respectively. Mesoporous TiO2 (mp-TiO2) paste is coated on GZO coated glass by …..Read More

Sajal Biring*畢少強, Annada Sankar Sadhu*, Moumita Deb

The development of a simple, low-cost sensor for the effective sensing of multiple gases in industrial or residential zones has been in high demand in recent days. In this article, we have proposed an optical sensor for the dual sensing of oxygen (O 2) and ammonia (NH 3) gases, which consists of oxygen and ammonia-sensitive fluorescent dyes coated individually on both sides of a glass substrate. An ethyl cellulose (EC) matrix doped with platinum (II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) serves as the oxygen …..Read More

Prashant Kumar Mishra, Somaditya Sen*, Ruhul Amin, Sajal Biring畢少強

ZnO is successfully synthesized by sol-gel synthesis route. These are analyzed by XRD, FESEM, and UV Sensing measurements. XRD indicates a polycrystalline nature with appreciable crystallinity. Changes in band structure and defect states are also discussed. Defect states are found to increase with annealing temperature and hence increase in oxygen related defects also noticed. Photocurrent decreases with annealing temperature. It may have wide applications in UV-sensors, UV filters, ad UV absorptive membranes etc...Read More

Piyali Maity, Satya Veer Singh, Sajal Biring畢少強, Bhola Nath Pal*, Anup K Ghosh*

Journal of Materials …, 2019 - pubs.rsc.org … devices with strong detectivity in the NIR region is preferentially required to selectively absorb NIR … This heterojunction photodetector shows high, selective NIR sensitivity which is not observe..Read More

Shin-Yu Wang, Chih-Ping Chen陳志平, Chung-Lin Chung, Chun-Wen Hsu, Hsiang-Lin Hsu, Ting-Hsuan Wu, Jia-Ying Zhuang, Chia-Jui Chang, Hao Ming Chen, Yuan Jay Chang

In this study, we synthesized four acceptor–donor–acceptor type hole-transporting materials (HTMs) of SY1–SY4 for an HTMs/interfacial layer with carbazole as the core moiety and ester/amide as the acceptor unit. These HTMs contain 4-hexyloxyphenyl substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene and thiophene units at the 3, 6-positions of the carbazole. When using amide-based HTMs SY2 as a dopant- free HTM in ap–i–n perovskite solar cell (PSC), we achieved a power conversion efficiency …..Read More

Kai-Ting Huang, Chien-Chung Shih, Bing-Huang Jiang, Ru-Jong Jeng, Chih-Ping Chen陳志平and Wen-Chang Chen

In this study, we first revealed green materials–poly-lysines (poly-L-lysine and poly-L-lysine blend poly-D-lysine)–as electron-extraction layers (EELs) in organic photovoltaics (OPVs). The distinct configurations of poly-lysine enantiomers were verified by conducting zeta potential analysis, and their work function (WF)-tuning capabilities for indium tin oxide (ITO) were affirmed by ultraviolet photoelectron spectroscopy (UPS). These two poly-lysine groups, with different arrangements of the amino groups that built up different surface …..Read More

Yang-Yen Yu*, Ching Tseng, Wei-Chen Chien, Hsiang-Lin Hsu, Chih-Ping Chen*陳志平

Poly (amic acid)(PAA) and polyimide (PI) can interact with Pb2+ and methylammonium halide by forming Lewis acid–base adducts and hydrogen bonds, respectively. These interactions can passivate perovskite (PVSK) defects and enhance PVSK solar cell (PSC) performance. Here, PAA and PI polymers were used as PSC additives by using pin PSC [ITO/NiO x/CH3NH3PbI3/with or without PAA or PI/PC61BM/BCP/Ag], and PVSK's interactions with PAA or PI were explored through X-ray photoelectron, UV–visible …..Read More

Chih-Hsin Chen* , Yu-Ting Hsu, Bo-Cheng Wang, Chung-Lin Chung, and Chih-Ping Chen*陳志平

In this study, a series of 2, 2′ and 3, 3′ substituted thienoisoindigo (TII)-based small molecules (H3–H7) were synthesized by using 1, 3-di (9 H-carbazol-9-yl) benzene, N- phenylcarbazole, triphenylamine, and benzene as electron donor (D) at the periphery, while TII as electron acceptor (A) at the core. The highest occupied molecular orbital energy levels of H3–H7 range from− 5.31 to− 5.43 eV, while their lowest unoccupied molecular orbital energy levels range from− 3.43 to− 3.59 eV. Under AM 1.5 condition, the perovskite solar …..Read More

Chun-Kai Wang, Bing-Huang Jiang, Yu-Wei Su, Ru-Jong Jeng, Yu-Jian Wang, Chih-Ping Chen*陳志平, and Ken-Tsung Wong

In this study, we synthesized 5, 11-dihexyl-4, 4, 10, 10-tetraoctylbenzo [1, 2-b: 4, 5-b′] bisthieno [4 ″, 5 ″-b ″: 4‴, 5‴-b‴] silolo [2 ″, 3 ″-d: 2‴, 3‴-d′] thiophene (ArSi) as a ladder-type electron-rich core for the preparation of three acceptor–donor–acceptor-type nonfullerene acceptors (NFAs)—ArSiID, ArSiID-F, and ArSiID-Cl—featuring (3-oxo-2, 3- dihydro-1 H-inden-1-ylidene) malononitrile (ID), 2-(5, 6-difluoro-3-oxo-2, 3-dihydro-1 H- inden-1-ylidene) malononitrile (ID-F), and 2-(5, 6-dichloro-3-oxo-2, 3-dihydro-1 H-inden-1 …..Read More

ing-Chieh Chao, Yu-Hua, Liao, Hsiang-Lin Hsua, Bing-Huang Jiang, Jui-Chih, Kao, Tai-Hong Lai, Chih-Ping Chen*陳志平, and Ru-Jong Jeng

In this study, we developed a star-shaped diketopyrrolopyrrole (DPP)-based additive as an efficient morphology fixing agent for organic photovoltaics (OPVs). This conjugated small molecule, DPPTPTA, has four arms, with two terphenyl units and four alkyl azide groups. We tested the behavior of DPPTPTA after incorporating it into an active layer comprising poly [4, 8-bis (5-(2-ethylhexyl) thien-2-yl) benzo [1, 2-b; 4, 5-b′] dithiophene-2, 6-diyl-alt-(4-(2- ethylhexyl)-3-fluorothieno [3, 4-b] thiophene)-2-carboxylate-2, 6-diyl)](PTB7-Th) and the …..Read More

D. Y. Lin*, B. C. Guo, Z. Y. Dai, C. F. Lin, and H. P. Hsu許宏彬,

In this work, we used the chemical vapor transport (CVT) method to grow PbI 2 crystals using iodine as a self-transporting agent. The crystals' structure, composition, and uniformity were confirmed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) measurements. We investigated the band gap energy using absorption spectroscopy measurements. Furthermore, we explored the temperature dependence of the band gap energy, which shifts from 2.346 eV at 300 K to 2.487 eV at 20 K, and extracted the …..Read More

H. P. Hsu許宏彬, D. Y. Lin*, J. J. Jheng, P. C. Lin, T. S. Ko

The optical properties of WSe 2-layered crystals doped with 0.5% niobium (Nb) grown by the chemical vapor transport method were characterized by piezoreflectance (PzR), photoconductivity (PC) spectroscopy, frequency-dependent photocurrent, and time-resolved photoresponse. With the incorporation of 0.5% Nb, the WSe 2 crystal showed slight blue shifts in the near band edge excitonic transitions and exhibited strongly enhanced photoresponsivity. Frequency-dependent photocurrent and time-resolved photoresponse …..Read More

J. S. Wu, D. Y. Lin*, Y. G. Li, H. P. Hsu許宏彬, M. C. Kao, H. Z. Chen

GaAs pin solar cells are studied using electroreflectance (ER) spectroscopy, light beam induced current (LBIC) mapping and photovoltaic characterization. Using ER measurements, the electric field across the pn junction of a wafer can be evaluated, showing 167 kV/cm and 275 kV/cm in the built-in condition and at− 3 V reverse bias, respectively. In order to understand the effect of the interval between metal grids on the device's solar performance, we performed LBIC mapping and solar illumination on samples of different …..Read More

Jui-Ju Hsiao, Yi-Jen Huang, Hung-Ing Chen, Joe-Air Jiang, Jen-Cheng Wang, Ya-Fen Wu吳亞芬, and Tzer-En Nee*

The intensive measures of luminescence in a GaN/InGaN multiple quantum well system are used to examine the thermodynamics and phenomenological structure. The radiative/nonradiative transitions along with absorbed or emitted phonons that occur between the different quantum states of the electrons and holes associated with these processes make the quantum efficiency of a semiconductor nanosystem in an equilibrium state an extensive property. It has long been recognized that tuning of the indium (In) …..Read More

Cheng-Shane Chu*朱承軒 and Meng-Wei Hsieh,

This paper presents a new optical fiber carbon dioxide (CO_2) sensor based on the emission wavelength shift of CuInS_2/ZnS quantum dots (CIS/ZnS QDs) due to changes in the absorption of a pH indicator (α-naphtholphthalein) with a changing CO_2 concentration. Using an LED with a central wavelength of 375 nm as the excitation source, it is shown that using the red emission of CIS/ZnS QDs allows for the detection of CO_2 concentration over the range of 0-100%, and the associated wavelength shift was found to be 630 pm/% CO_2 …..Read More

Zong-Liang Tseng曾宗亮, Chien-Hung Chiang, Chun-Guey Wu*

Perovskite solar cells (PSCs) are one of the highly promising new‐generation photovoltaic technologies. One of the remaining challenges for commercializing PSCs is to prepare high‐ quality, large‐area perovskite films in an ambient atmosphere reproducibly using less toxic materials. Herein, a nonvolatile, less toxic substance, 2‐pyrrolidinone (2P), is used as a complexant solvent for the perovskite precursor solution. Combining this with a newly developed spin‐assisted solvent extraction (SASE) crystallization method, a high‐quality …..Read More

Sheng Hsiung Chang*, Sheng-De Wong, Hsiu-Ying Huang, Chi-Tsu Yuan, Jia-Ren Wu, Shou-En Chiang, Zong-Liang Tseng曾宗亮, Sheng-Hui Chen

Abstract CH 3 NH 3 PbI 3 (MAPbI 3) perovskite thin films were fabricated by using the one- step spin-coating method with a washing-enhanced nucleation (WEN) process under various dropping times, and the resultant thin films were characterized through the reflected- type optical microscope, atomic force microscope, transmittance spectrometer, X-ray diffractometer, photoluminescence spectrometer and water droplet contact-angle imaging system. The experimental results show that the dropping time for the WEN process strongly …..Read More

Lung-Chien Chen, Zong-Liang Tseng曾宗亮*, Chun-Cheng Lin

In this study, a low-temperature sol–gel deposited ZnO thin film was used as an electron- transport layer in planar type CH3NH3PbI3 perovskite-based solar cells. The devices based on ZnO were coated on glass and flexible substrates were compared and discussed. The results show that we can achieve a record efficiency of 13.5%(glass) and 10.2%(PET) under AM1. 5G irradiation for the low-temperature prepared ZnO based planar type perovskite solar cell...Read More

Chun-Cheng Lin, Zong-Liang Tseng*曾宗亮, Lung-Chien Chen

Contour-mode thin-film bulk acoustic-wave resonators (TFBARs) incorporating a 4.5 at% Li- doped ZnO (LZO) film are fabricated on Si substrates using a radio frequency (RF) magnetron sputtering process followed by ultraviolet (UV)-ozone illumination for 30, 60 and 90 min, respectively. The effects of the post-treatment time on the microstructural, piezoelectric and binding energy properties of the various films are systematically explored. It is found that the LZO films have a predominantly c-axis orientation. In addition, the largest …..Read More

Ching-Ho Tien, Lung-Chien Chen*, Kun-Yi Lee, Zong-Liang Tseng*曾宗亮, Yu-Shen Dong, Zi-Jun Lin,

High-quality perovskite CsPbBr 3 quantum dots (QDs-CsPbBr 3) were prepared using the ultrasonic oscillation method, which is simple and provides variable yield according to requirements. The emission spectra over a large portion of the visible spectral region (450– 650 nm) of QD-CsPbX 3 (X= Cl, Br, and I) have tunable compositions that can be halide exchanged using the halide anion exchange technique and quantum size-effects. A strong peak with high intensity of (200) lattice plane of purified QDs-CsPbBr 3 film is obtained …..Read More

Lung-Chien Chen*, Ching-Ho Tien, Sin-Liang Ou, Kun-Yi Lee, Jianjun Tian*, Zong-Liang Tseng曾宗亮, Hao-Tian Chen, Hao-Chung Kuo, An-Cheng Sun,

Abstract Perovskite CsPbBr 3 quantum dot (CsPbBr 3-QD) recovery was performed using lead scrap from lead storage batteries. The perovskite CsPbBr 3-QD characteristics were analyzed using different PbO/recycled PbO 2 ratios. Scanning electron microscopy (SEM) was used to observe the film surface morphology and cross-section. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to observe the perovskite CsPbBr 3-QDs' structural characteristics. A photoluminescence (PL) …..Read More

Lung-Chien Chen*, Ching-Ho Tien, Zong-Liang Tseng曾宗亮, Yu-Shen Dong, Shengyi Yang*

The poor stability of CsPbX 3 quantum dots (QDs-CsPbX 3) under wet conditions is still considered to be a key issue. In order to overcome this problem, this study presents a high molecular weight polymer matrix (polymethylmethacrylate, PMMA) incorporated into the QDs- CsPbBr 3 to improve its stability and maintain its excellent optical properties. In this study, the Cs 2 CO 3, PbO, Tetrabutylammonium Bromide (TOAB) powder, oleic acid, and toluene solvent were uniformly mixed and purified to prepare high-quality QDs powders. Then …..Read More

Lung-Chien Chen*, Ching-Ho Tien, Zong-Liang Tseng*曾宗亮, Jun-Hao Ruan

We describe a method to enhance power conversion efficiency (PCE) of MAPbI 3 perovskite solar cell by inserting a FAPbX 3 perovskite quantum dots (QD-FAPbX 3) layer. The MAPbI 3 and QD-FAPbX 3 layers were prepared using a simple, rapid spin-coating method in a nitrogen-filled glove box. The solar cell structure consists of ITO/PEDOT: PSS/MAPbI 3/QD- FAPbX 3/C 60/Ag, where PEDOT: PSS, MAPbI 3, QD-FAPbX 3, and C 60 were used as the hole transport layer, light-absorbing layer, absorption enhance layer, and electron transport …..Read More

Yu-Ching Huang*黃裕清, Wei-Shin Liu, Cheng-Si Tsao*, Leeyih Wang

Thermal stability is a bottleneck toward commercialization of polymer solar cells (PSCs). The effect of PCBM aggregation on a multilength scale on the bulk-heterojunction (BHJ) structure, performance, and thermal stability of PSCs is studied here by grazing-incidence small-and wide-angle X-ray scattering. The evolution of hierarchical BHJ structures of a blend film tuned by regioregularity of polymers from the as-cast state to the thermally unstable state is systematically investigated. The thermal stability of PSCs with high polymer …..Read More

Yu-Ching Huang*黃裕清, De-Han Lu, Chia-Feng Li, Cheng-Wei Chou, Hou-Chin Cha, and Cheng-Si Tsao

The aim of this study is to mitigate the loss of performance of organic photovoltaics when the device area is increased. We propose that performance reduction is a result of the poor transverse charge transport due to defects in the electron transport layer and the resistance of the transparent electrode. We modified the surface of a zinc oxide (ZnO) with ethoxylated polyethylenimine and successfully lowered the performance reduction from 30% to 15% based on two electron transport layers of ZnO and ethoxylated polyethylenimine (PEIE) …..Read More

Yu-Ching Huang*黃裕清, Chia-Feng Li, Zhi-Hao Huang, Po-Hung Liu, and Cheng-Si Tsao

A nitrogen-free and slot-die coating fabrication of perovskite solar cells combined with NIR annealing. We develop a fabrication approach of planar inverted structured perovskite solar cell (PSC) in ambient condition with a PCE of 12.4% as compared to that (13.3%) of PSC fabricated in glove box filled with nitrogen. In addition, we demonstrate an alternative post- annealed method by near-infrared (NIR) radiation to traditional heating method by oven. The annealed time by NIR can be shortened from 1500 s to 30 s and the device performance …..Read More

Yun-Ming Sung, Yu-Ching Huang*黃裕清, Forest Shih-Sen Chien, Cheng-Si Tsao

In this study, we focus on the analysis of thermal burn-in degradation behavior of organic photovoltaics (OPVs) at 85° C under nitrogen atmosphere. In this thermal aging as the accelerated test, the thermal burn-in loss (initially rapid drop) in the power conversion efficiency (PCE) of the inverted OPV devices based on ITO/ZnO/PTB7: PC 71 BM/MoO 3/Ag was shown over 40% PCE reduction. We systematically investigate the effects of bulk heterojunction structure and Ag electrode on thermal degradation. Moreover, we adopt two ..Read More

Hung-Yu Lin, Chien-Yu Chen, Bo-Wei Hsu, Yu-Lun Cheng, Wei-Lun Tsai, Yu-Ching Huang黃裕清, Cheng-Si Tsao, and Hao-Wu Lin

In this study, we focus on the analysis of thermal burn-in degradation behavior of organic photovoltaics (OPVs) at 85° C under nitrogen atmosphere. In this thermal aging as the accelerated test, the thermal burn-in loss (initially rapid drop) in the power conversion efficiency (PCE) of the inverted OPV devices based on ITO/ZnO/PTB7: PC 71 BM/MoO 3/Ag was shown over 40% PCE reduction. We systematically investigate the effects of bulk heterojunction structure and Ag electrode on thermal degradation. Moreover, we adopt two ..Read More

Nguyen HC, Ong HC, Pham TTT, Dinh TKK, Su CH*蘇家弘

This study developed a new catalyst‐free process for producing ethyl levulinate, a biofuel additive. Noncatalytic levulinic acid esterification with ethanol using microwave irradiation (MW) was compared with that using traditional heating (TH) under different reaction conditions. The results demonstrated that the esterification process using MW was more effective than that using TH. A reaction conversion of 90.38% was obtained for the esterification using MW at 473 K and reaction time of 3 hours. Moreover, this study …..Read More

Wang X, Huang YT, Liu C, Mu KY, Li KH, Wang SJ, Yang Y, Wang L, Su CH蘇家弘, Feng SP*

Efficient low-grade heat recovery can help to reduce greenhouse gas emission as over 70% of primary energy input is wasted as heat, but current technologies to fulfill the heat-to- electricity conversion are still far from optimum. Here we report a direct thermal charging cell, using asymmetric electrodes of a graphene oxide/platinum nanoparticles cathode and a polyaniline anode in Fe 2+/Fe 3+ redox electrolyte via isothermal heating operation. When heated, the cell generates voltage via a temperature-induced pseudocapacitive effect of …..Read More

Wang FM*, Alemu T, Yeh NH, Wang XC, Lin YW, Hsu CC, Chang YJ, Liu CH, Chuang CI, Hsiao LH, Chen JM, Haw SC, Chen WL, Pham QT, Su CH蘇家弘

Self-terminated oligomer additives synthesized from bismaleimide and barbituric acid derivatives improve the safety and performance of lithium-ion batteries (LIBs). This study investigates the interface interaction of these additives and the cathode material. Two additives were synthesized by Michael addition (additive A) and aza-Michael addition (additive B). The electrochemical performances of bare and modified LiNi0. 6Mn0. 2Co0. 2O2 (NMC622) materials are studied. The cycling stability and rate capability of NMC622 …..Read More

Kahsay BA, Ramar A, Wang FM*, Yeh NH, Lin PL, Luo ZJ, Chan TS, Su CH蘇家弘

Polyisothianaphthene has the smallest bandgap among all conjugated polymers and delivers high electrical conductivity. This study uses polyisothianaphthene as an active material to accept both lithium ions and PF 6− on its cyclic C–S–C bond and benzene ring during the processes of n-doping and p-doping. This study discovers that lithium polysulfide and lithium sulfide are formed during the first electrochemical reaction; however, the impedance, rate performance, and energy density of polyisothianaphthene cells are not …..Read More

Tesemma M, Wang FM*, Haregewoin AM, Hamidah NL, Hendra PM, Lin SD*, Chern CS*, Pham QT, Su CH蘇家弘

Bismaleimides modified through fluorosubstitution constitute two new electrolyte additives that have been successfully synthesized and used in lithium ion batteries. Fluorosubstitution significantly eliminates the interface impedances of the two electrodes and improves the rate performance of batteries because of the reduced LiF and Li2CO3 content in a solid electrolyte interphase. This study indicates that between the symmetric (two fluorosubstitutions) and asymmetric (one fluorosubstitution) designs of fluorosubstitution in …..Read More

Publications 2018

Tzu-Hung Yeh, Chih-Chien Lee, Chun-Jen Shih, Gautham Kumar, Sajal Biring, Shun-Wei Liu

We report a highly efficient transparent and inverted organic light-emitting diode (OLED) with a vacuum-deposited MoO 3 (5 nm)/Ag (12 nm)/WO 3 (40 nm)(MAW) multilayered electrode having a low sheet resistance of 4.2 Ω/sq, an average transmittance of 88% at a wavelength of 500–550 nm, and a smooth morphology with a root-mean-square roughness of 0.339 nm. The inverted phosphorescent OLED with MAW anode exhibits a total (sum of the bottom and top emissions) maximum power efficiency of 62.1 lm/W and an external quantum efficiency of 20.1%. In addition, the transparent device can achieve almost equal bottom-to-top emission ratio of 1: 1.1 and a total transmittance of> 80% in the visible-light range. The better device performance arises from the transparent MAW electrode acting as a capping layer to modulate the bottom/top emission direction and the optical properties of the device. ...Read More

Tulika Srivastava, Gaurav Bajpai, Shun Wei Liu, Sajal Biring, Somaditya Sen

Abstract Effect of different wavelengths (350, 380, 390, 400, 450, 550 & 650 nm) of light on surface conductivity of sol-gel synthesized Zn 1− x Si x O material has been observed. Enhancement in conductivity at all wavelengths of light had been attributed to enhanced charge carrier concentration with silicon doping. Reduction in sensitivity for UV and visible light wavelength indicates reduction of surface defects and deep level traps with Si 4+ incorporation. Enhanced photo stability with Si 4+ doping makes it an appropriate material for transparent electrodes used in various display and electronic devices...Read More

Anita Verma, Arun Kumar Yadav, Sunil Kumar, Velaga Srihari, Parasmani Rajput, V Raghavendra Reddy, Ravindra Jangir, Himanshu K Poshwal, Shun Wei Liu, Sajal Biring, Somaditya Sen

A detailed study was carried out to investigate the effects of poling on structure, vibrational, dielectric, and ferroelectric properties of donor-doped (V5+ at Ti4+-site) lead-free Na0. 47Bi0. 47Ba0. 06Ti (1-x) VxO3,(x= 0, 0.01, and 0.03) ceramics fabricated via a modified sol- gel method. Rietveld refinement of synchrotron radiation source powder x-ray diffraction data showed that unpoled samples are in rhombohedral R3c phase whereas poled samples showed a mix rhombohedral R3c and tetragonal P4mm phases at ambient temperature, due to a long-range order established in lattice system after poling. V+ 5 doping increases the rhombohedral distortion in unpoled and poled samples while it reduces the tetragonality in poled samples. Vibrational study revealed that unpoled samples have more lattice disorder compared to poled samples. X-ray absorption near edge spectroscopy measurement …..Read More

Anita Verma, Arun Kumar Yadav, Nasima Khatun, Sunil Kumar, Ravindra Jangir, Velaga Srihari, V Raghavendra Reddy, Shun Wei Liu, Sajal Biring, Somaditya Sen

The structural, dielectric and ferroelectric properties of lead-free (Na0. 5-xKxBi0. 5-xLax) TiO3 powders synthesized by sol-gel self-combustion method were investigated. Rietveld refinement of Synchrotron x-ray diffraction data confirms pure single phase rhombohedral crystal structure with R3c space group for all the compositions and anti-phase octahedral tilting angle decreased with increase in composition x. Homogeneity and elemental proportions were confirmed by Energy dispersive x-ray spectrometry. The temperature- dependent dielectric study has shown two diffuse type of dielectric anomaly for all the samples, due to A-site disorder in the lattice, which has been assigned to two-has transitions: ferroelectric to anti-ferroelectric and anti-ferroelectric to the paraelectric phase transition. The transition temperature of these phase transitions is found to decrease as a …..Read More

Shun-Wei Liu, Sajal Biring, Ya-Ze Li, Ken-Tsung Wong

A novel up‐conversion device for NIR image sensing is proposed by integrating the OLED, OPV, and transparent electrodes. The proposed device captures NIR light reflected from the object and forms a real‐time image at the visible wavelengths on the OLED display with the image quality of> 600 dpi...Read More

Tulika Srivastava, Gaurav Bajpai, Gyanendra Rathore, Shun Wei Liu, Sajal Biring, Somaditya Sen

The UV sensing in pure ZnO is due to oxygen adsorption/desorption process from the ZnO surface. Vanadium doping improves the UV sensitivity of ZnO. The enhancement in UV sensitivity in vanadium-substituted ZnO is attributed to trapping and de-trapping of electrons at V4+ and V5+-related defect states. The V4+ state has an extra electron than the V5+ state. A V4+ to V5+ transformation happens with excitation of this electron to the conduction band, while a reverse trapping process liberates a visible light. An analytic study of response phenomenon reveals this trapping and de-trapping process...Read More

Arun Kumar Yadav, Anita Verma, Sunil Kumar, Velaga Srihari, AK Sinha, V Raghavendra Reddy, Shun Wei Liu, Sajal Biring, Somaditya Sen

The phase purity and crystal structure of Pb (1-x) LaxTi (1-x) AlxO3 (0≤ x≤ 0.25) samples (synthesized via the sol-gel process) were confirmed using synchrotron x-ray powder diffraction (XRD)(wavelength, λ= 0.44573 Å). Rietveld analyses of powder x-ray diffraction data confirmed the tetragonal structure for compositions with x≤ 0.18 and cubic structure for the sample with x= 0.25. Temperature-dependent XRD was performed to investigate the structural change from tetragonal to cubic structure phase transition. Raman spectroscopy at room temperature also confirmed this phase transition with compositions. Field emission scanning electron microscopy (FESEM) provided information about the surface morphology while an energy dispersive x-ray spectrometer attached with FESEM confirmed the chemical compositions of samples. Temperature and frequency dependent dielectric studies …..Read More

Tulika Srivastava, Gaurav Bajpai, Gyanendra Rathore, Prashant Mishra, Shun Wei Liu, Sajal Biring, Somaditya Sen

ZnO is co-doped with Na+ and Si4+ in the ratio 2: 1. The ratio was intentionally chosen so that net valence state of dopant theoretically matches that of host. This is to avoid dependence in the amount of oxygen vacancies/interstitials arising out of cationic valence state of the dopant. With such a combination, modifications in structural and optical properties do not depend on excess or deficit of the dopant charge state. For lower doping, Na+ ions behave as interstitial sites which enhance strain, lattice disorder and thereby creating defects. Formation of interstitial defects leads to reduction in bandgap energy and produce orange-red luminescence. For higher doping, Na+ starts substituting at Zn2+ site which helps in reducing strain and lattice disorder and thereby increases bandgap. Inspite of presence of Si4+ with higher charge, there is a gradual increase in oxygen vacancies due …..Read More

Arun Kumar Yadav, Anita Verma, Birender Singh, Deepu Kumar, Sunil Kumar, Velaga Srihari, Himanshu K Poshwal, Pradeep Kumar, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Structural, vibrational and dielectric properties of (Pb1-xBix)(Ti1-xMnx) O3 (PBTM)(0 x 0.50) polycrystalline ceramics have been examined as a function of temperature. Synchrotron- based powder x-ray diffraction was employed to confirm phase purity and crystal structure of samples. Tetragonality (c/a ratio) of the PBTM system exhibit an increase 1.065, 1.066 for x= 0.06 and 0.09 compositions respectively, compare to 1.064 for x= 0 sample. Curie point was found~ 763 K and 773 K for x= 0.06 and 0.09 samples respectively. Though, tetragonality start to decreasing from samples with x 0.18, Curie point of the samples started decreasing for x 0.12. Temperature-dependent x-ray diffraction reveals the structural change from tetragonal to cubic structure. Unit cell volume was found to decrease with increasing temperature; indicate these materials are negative thermal expansion type until phase …..Read More

A Venkateswararao, Shun-Wei Liu, Ken-Tsung Wong

In organic solar cells (OSCs), the electron donor (D) and electron acceptor (A) blended active layer is the most crucial component for governing the power conversion efficiency (PCE). Various efficient donor materials with wide structural variations have been developed to couple with high-electron mobility fullerene-based acceptors, giving PCEs beyond 12%. However, fullerene-embedded OSCs encounter great challenges of low flexibility for structural modifications, poor absorption and blend morphological stability. The demand for alternative acceptors drives current OSC research towards non-fullerene acceptors (NFAs). Tailor-made NFAs of polymer or small molecule (SM) can typically exhibit tunable optical and electrochemical properties, high solubility, air stability, and favorable intermolecular interactions leading to compact packing and good nano-phase segregation in the active …..Read More

Chun-Jen Shih, Chih-Chien Lee, Ying-Hao Chen, Sajal Biring, Gautham Kumar, Tzu-Hung Yeh, Somaditya Sen, Shun-Wei Liu, Ken-Tsung Wong

An exciplex forming cohost system is employed to achieve a highly efficient organic light- emitting diode (OLED) with good electroluminescent lifetime. The exciplex is formed at the interfacial contact of a conventional star-shaped carbazole hole-transporting material, 4, 4′, 4 ″-tris (N-carbazolyl)-triphenylamine (TCTA), and a triazine electron-transporting material, 2, 4, 6-tris [3-(1 H-pyrazol-1-yl) phenyl]-1, 3, 5-triazine (3P-T2T). The excellent combination of TCTA and 3P-T2T is applied as the cohost of a common green phosphorescent emitter with almost zero energy loss. When Ir (ppy) 2 (acac) is dispersed in such exciplex cohost system, OLED device with maximum external quantum efficiency of 29.6%, the ultrahigh power efficiency of 147.3 lm/W, and current efficiency of 107 cd/A were successfully achieved. More importantly, the OLED device showed a low-efficiency roll-off and an …..Read More

Anand Sharma, Nitesh K Chourasia, Anumol Sugathan, Yogesh Kumar, Satyabrata Jit, Shun-Wei Liu, Anshu Pandey, Sajal Biring, Bhola N Pal

Li5AlO4, a well-known material for solid state electrolyte application, has never been considered hitherto as a gate dielectric of metal oxide thin film transistors (TFTs). Here we demonstrate the salient features of Li5AlO4 as a gate dielectric outperforming the conventional inorganic dielectrics used in TFTs. The high dielectric constant (k) of this insulator has been achieved by utilizing the improved capacitance contributed by mobile lithium ions (Li+) within the dielectric film. We have synthesized this dielectric via a cost- effective sol–gel method followed by a low-temperature annealing process yielding three phases such as amorphous-Li5AlO4 (a-Li5AlO4), α-Li5AlO4, and β-Li5AlO4 under different annealing conditions. Optimized TFTs fabricated with all of these three phases of Li5AlO4 on top of a highly doped silicon (p++-Si) wafer and a solution processed semiconducting …..Read More

Ko-Wei Chen, Li-Yen Lin, Yi-Hua Li, Ya-Ze Li, Thanh Phuc Nguyen, Sajal Biring, Shun-Wei Liu, Ken-Tsung Wong

Four new molecules with acceptor-donor-acceptor (ADA) configuration where cyclopenta [2, 1-b: 3, 4-b′] dithiophene (CPDT) as the electron-donating core connecting to cyano (CN)- substituted 2, 1, 3-benzothiaidiazole (BT) as electron-withdrawing end groups are reported. With the same acceptor CN-BT, we found that CPDT can serve as a better donor as compared to that of dithieno [3, 2-b: 2′, 3′-d] silole (DTS) to give stronger intramolecular charge transfer (ICT) character and therefore better light harvesting ability. The number and orientation of F-substitution on the BT ring, giving a clear structure-property relationship, can subtly manipulate the physical characteristics. These ADA type molecules were employed as electron donor in conjunction with C 70 as the electron acceptor in vacuum-deposited bulk heterojunction (BHJ) small-molecule organic solar cells (SMOSCs). Among them, the …..Read More

Alakesh Bera, Sajal Biring

Binding of recombinant prion protein with small highly structured RNAs, prokaryotic and eukaryotic prion protein mRNA pseudoknots, tRNA and polyA has been studied by the change in fluorescence anisotropy of the intrinsic tryptophan groups of the protein. The affinities of these RNAs to the prion protein and the number of sites where the protein binds to the nucleic acids do not vary appreciably although the RNAs have very different compositions and structures. The binding parameters do not depend upon pH of the solution and show a poor co-operativity. The reactants form larger nucleoprotein complexes at pH 5 compared to that at neutral pH. The electrostatic force between the protein and nucleic acids dominates the binding interaction at neutral pH. In contrast, nucleic acid interaction with the incipient nonpolar groups exposed from the structured region of the prion protein …..Read More

Saurabh Tiwari, Nivedha Balasubramanian, Sajal Biring, Somaditya Sen

Sol-gel synthesized nanocrystalline Co doped CeO2 powders [(Ce1-xCoxO2; x= 0, 0.03)] were made into cylindrical discs by uniaxial pressing and sintered at 1500° C for 24h to measure mechanical properties. The pure phase formation of undoped and Co doped samples were confirmed by X-ray diffraction and Raman analysis. The scanning electron microscopy (SEM) was used for observing the microstructure of sintered samples to investigate density, porosity, and grain size. The grains size observed for 1500° C sintered samples 5-8 µm. Vickers indentation method used for investigating the micro-hardness. For undoped CeO2 micro-hardness was found 6.2 GPa which decreased with Co doping. It was found that samples follow indentation size effect (ISE) and follow elastic than plastic deformation. Enhanced ductile nature with Co doping in CeO2 made it more promising …..Read More

Gaurav Bajpai, Tulika Srivastava, Faizan Husian, Sunil Kumar, Sajal Biring, Somaditya Sen

Structural, optical, and photoluminescence properties of Zn 0.95 Si 0.05− x Fe x O (0≤ x≤ 0.05) nano-crystallites prepared by sol-gel process has been investigated thoroughly revealing enhanced red emission in co-doped samples originating from oxygen interstitials. Greater ionic charge and smaller size of the substituent ions helps generate more interstitials forming defect states within the bandgap. The correlation between oxygen interstitials, ie defect states corresponding to the doping concentrations of Si and Fe ions and the enhanced red emissions from the samples has been established unequivocally following a quantitative approach by analyzing the photoluminescence spectra contributed from the individual defect levels...Read More

Alakesh Bera, Sajal Biring

Different studies indicated that the prion protein induces hybridization of complementary DNA strands. Cell culture studies showed that the scrapie isoform of prion protein remained bound with the chromosome. In present work, we used an oxazole dye, YOYO, as a reporter to quantitative characterization of the DNA condensation by prion protein. We observe that the prion protein induces greater fluorescence quenching of YOYO intercalated in DNA containing only GC bases compared to the DNA containing four bases whereas the effect of dye bound to DNA containing only AT bases is marginal. DNA-condensing biological polyamines are less effective than prion protein in quenching of DNA-bound YOYO fluorescence. The prion protein induces marginal quenching of fluorescence of the dye bound to oligonucleotides, which are resistant to condensation. The ultrastructural studies …..Read More

Palaniyandi Velusamy, Chaitra Megaravalli Srinivasa, Govindarajan Venkat Kumar, Yasrib Qurishi, Chia-Hung Su, Subash CB Gopinath

Mesoporous silica nanoparticles (MSN) have been attracted in the field of biomedicine due to their versatile properties as a drug nanocarrier. In this research, MSN and thiol modified MSN (mMSN) were synthesized to be the drug nanocarriers, by the sol–gel technique for the efficient delivering doxorubicin hydrochloride (DOX). These carriers were characterized by Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM), SA3100 analyzer (Brunauer–Emmett–Teller), Zetasizer and Fourier transform infrared spectroscopy (FTIR). FESEM observation revealed that these particles have uniform sizes and the zeta potential analysis confirmed the existence of surface charge and stability of the particles. Brunauer–Emmett–Teller showed that MSN and mMSN are characteristic type IV N 2 adsorption/desorption patterns. The in vitro drug release profile studies have …..Read More

Hoang Chinh Nguyen, Chia-Hung Su, Yuan-Kun Yu, Dinh Thi My Huong

Oleaginous microalgae are known as promising oil producers, which accumulate high amount of lipids from various carbon substrates. This study first investigated sugarcane bagasse hydrolysate as a cheap carbon source for the production of biomass and lipid by Schizochytrium sp. The sugarcane bagasse was pretreated with alkali followed by phosphoric acid to remove lignin and enhance xylose production, respectively. The enzymatic hydrolysis of the pretreated sugarcane bagasse by cellulase was subsequently optimized. A maximum glucose yield of 95.77% was obtained at an enzyme loading of 0.3 mL/g with a hydrolysis reaction time of 48 h. The sugarcane bagasse hydrolysate containing glucose and xylose was subsequently used as a substrate for cultivating Schizochytrium sp. Results showed that sugarcane bagasse hydrolysate performed better than refined …..Read More

Hoang Chinh Nguyen, Shih-Hsiang Liang, Sing-Ying Li, Chia-Hung Su, Chien-Chung Chien, Yi-Ju Chen, Dinh Thi My Huong

In this study, direct transesterification with a combination of methanol and a cosolvent was demonstrated to be promising for the production of biodiesel from black soldier fly larvae (BSFL) biomass. Of the solvents tested, n-hexane was identified as the most effective cosolvent for the reaction, resulting in a 14.5-fold increase in the biodiesel yield, compared with the reaction without a cosolvent. The direct transesterification using n-hexane as a cosolvent was then optimized to maximize the biodiesel yield. The highest biodiesel yield of 94.14% was achieved at an n-hexane: methanol volume ratio of 1: 2 (v/v), a solvent dosage of 12 mL, a catalyst loading of 1.2 mL, a temperature of 120° C, and a reaction time of 90 min. The properties of the BSFL biodiesel were also tested, and most—such as the biodiesel's density (875 kg/m 3), water content (0.03 mg/kg), ester content (98.3%), acid …..Read More

Raman Pachaiappan, Ekant Tamboli, Aurovind Acharya, Chia-Hung Su, Subash CB Gopinath, Yeng Chen, Palaniyandi Velusamy

Enzyme hydrolysates (trypsin, papain, pepsin, α-chymotrypsin, and pepsin-pancreatin) of Tinospora cordifolia stem proteins were analyzed for antioxidant efficacy by measuring (1) 1, 1-diphenyl-2-picrylhydrazyl (DPPH•) radical scavenging activity,(2) 2, 20-azinobis (3- ethylbenzothiazoline-6-sulfonic acid)(ABTS+) radical scavenging capacity, and (3) Fe2+ chelation. Trypsin hydrolysate showed the strongest DPPH• scavenging, while α- chymotrypsin hydrolysate exhibited the highest ABTS+ scavenging and Fe2+ chelation. Undigested protein strongly inhibited the gastrointestinal enzymes, trypsin (50% inhibition at enzyme/substrate ratio= 1: 6.9) and α-chymotrypsin (50% inhibition at enzyme/substrate ratio= 1: 1.82), indicating the prolonged antioxidant effect after ingestion. Furthermore, gel filtration purified peptide fractions of papain hydrolysates exhibited a significantly higher …..Read More

Hoang Chinh Nguyen, Shih-Hsiang Liang, Shang-Sian Chen, Chia-Hung Su, Jhih-Huei Lin, Chien-Chung Chien

Black soldier fly larvae (BSFL) are oleaginous insects that can assimilate organic waste for fat accumulation, and thus serve as an alternative feedstock for biodiesel production. In lipase-catalyzed transesterification, enzymes are deactivated by excess methanol. To address this obstacle, methyl acetate is suggested as an alternative acyl acceptor to methanol. In this study, methyl acetate was first used in the enzymatic production of biodiesel with BSFL as a triglyceride source. The interesterification of BSFL fat with methyl acetate was catalyzed using Novozym 435 as an efficient immobilized lipase. Response surface methodology was used to optimize the reaction and establish a reliable mathematical model for prediction. A maximum biodiesel yield of 96.97% was reached at a reaction time of 12 h, molar ratio of methyl acetate to fat of 14.64: 1, enzyme loading of …..Read More

Hoang Chinh Nguyen, Dinh Thi My Huong, Horng-Yi Juan, Chia-Hung Su, Chien-Chung Chien

Liquid lipase-catalyzed esterification of fatty acids with methanol is a promising process for biodiesel production. However, water by-product from this process favors the reverse reaction, thus reducing the reaction yield. To address this, superabsorbent polymer (SAP) was used as a water-removal agent in the esterification in this study. SAP significantly enhanced the conversion yield compared with the reaction without SAP. The lipase- catalyzed esterification in the presence of SAP was then optimized by response surface methodology to maximize the reaction conversion. A maximum conversion of 96.73% was obtained at a temperature of 35.25° C, methanol to oleic acid molar ratio of 3.44: 1, SAP loading of 10.55%, and enzyme loading of 11.98%. Under these conditions, the Eversa Transform lipase could only be reused once. This study suggests that the liquid lipase …..Read More

Cheng-Shane Chu, Chih-Jen Su

This paper presents a ratiometric optical broad range pH sensor that comprises an optical fiber coated at one end with CdSe/ZnS quantum dots (QDs) and Oxazine 170 perchlorate (O170) embedded in ethyl cellulose (EC) matrix. The feasibility of coating an optical fiber with the sensing film to fabricate a ratiometric fiber optic broad range pH sensor is investigated. Using an LED with a central wavelength 405 nm as an excitation light source, the CdSe/ZnS QDs shows that the fluorescence intensity at 575 nm decreases with increasing pH and O170 shows the fluorescence intensity at 655 nm increases with increasing pH. The ratio of fluorescence intensities at 575 and 655 nm has a linear relationship with pH value in the 1.6–13.2 range. The ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the …..Read More

Cheng-Shane Chu, Chih-Jen Su

In this study, a simple and cost-effective technique to fabricate a plastic optical fiber sensor for the dual sensing of hydrogen peroxide (H 2 O 2) and dissolved oxygen (DO) was described. The optical fiber dual sensor consisted of CdSe/ZnS core–shell quantum dots (QDs), with oxygen indicators coated on the fiber end of the sensor. An ethyl cellulose (EC) matrix doped with CdSe/ZnS QDs and tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II)(Ru (dpp) 3 2+) served as the sensing materials for H 2 O 2 and DO. The sensing materials for H 2 O 2 and DO were excited with an light emitting diode (LED) of 405 nm, and the two emission wavelengths were separately detected. The optical fiber dual sensor was applied for the monitoring of different H 2 O 2 and DO concentrations. The typical Stern– Volmer plot of an optical fiber dual sensor for the sensing of DO demonstrated linearity …..Read More

Chih-Ping Chen, Yi-Chan Li, Yao-Yu Tsai, Yu-Wei Lu

We have prepared an efficient ternary polymer solar cell incorporating a poly (indacenodithiophene)-based conjugated polymer (PIDTBT),[6, 6]-phenyl-C 71-butyric acid methyl ester (PC 71 BM), and 3, 9-bis (2-methylene-(3-(1, 1-dicyanomethylene) indanone)- 5, 5, 11, 11-tetrakis (4-hexylphenyl)-dithieno [2, 3-d: 2, 3-d]-s-indaceno [1, 2-b: 5, 6-b]- dithiophene (ITIC). Grazing-incidence wide-angle X-ray scattering (GIWAXS), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy revealed that intermolecular interactions between the PC 71 BM and ITIC units disrupted the formation of large ITIC crystals. The ITIC and PC 71 BM components formed compatible domains that dispersed well within the PIDTBT matrix, providing optimized ternary blends for efficient carrier transport and led to greater photon-to-electron conversion efficiency. Compared with the …..Read More

Tzong‐Yuan Juang, Jui‐Chih Kao, Jian‐Cheng Wang, Shuo‐Yen Hsu, Chih‐Ping Chen

In this study, water‐dispersed carbonized bamboo‐derived carbon nanodot (CND) is prepared through thermal dissociation followed by aqueous extraction. The CND exhibits high photoluminescence with a value of λem of 430 nm and a fluorescence quantum yield of 4.2%, a particle size of≈ 3–5 nm, and presents both COOH and OH functionalities. The CND serves as cathode interfacial layer that efficiently increases the power conversion efficiencies of both fullerene‐and nonfullerene‐based organic photovoltaics (OPVs). Embedding the CND alters the work function and surface roughness of the ZnO layer and, thereby, affects the morphologies of the active layers as well as the charge selectivity and transportation. The resulting increases in electron transport and extraction of the OPV devices lead to increases in the fill factor (FF) and short‐circuit current density (Jsc). The …..Read More

Hsiang-Lin Hsu, Ying-Chieh Chao, Yu-Hua Liao, Chung-Lin Chung, Ya-Juan Peng, Chih-Ping Chen, Ru-Jong Jeng

In this study, we prepared DPPBTDA, a diketopyrrolopyrrole-based small molecule presenting a terminal cross-linkable azido group, as a cathode modifying layer for organic photovoltaics (OPVs) having the inverted device structure glass/indium tin oxide/zinc oxide (ZnO) with or without the interfacial layer (IFL)/active layer/MoO3/Ag. The active layer comprising a blend of poly [4, 8-bis (5-(2-ethylhexyl) thien-2-yl) benzo [1, 2-b; 4, 5-b′] dithiophene-2, 6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno [3, 4-b] thiophene)-2-carboxylate-2, 6-diyl](PTB7-Th) as the electron donor and [6, 6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the electron acceptor. Atomic force microscopy, space-charge-limited current mobility, surface energy, electron spectroscopy for chemical analysis depth profile, ultraviolet photoelectron spectroscopy analysis, and OPV performance data revealed that …..Read More

Jong‐Hong Lu, Yi‐Hung Lin, Bing‐Huang Jiang, Chun‐Hung Yeh, Jui‐Chih Kao, Chih‐Ping Chen

High‐performance colored aesthetic semitransparent organic photovoltaics (OPVs) featuring a silver/indium tin oxide/silver (Ag/ITO/Ag) microcavity structure are prepared. By precisely controlling the thickness of the ITO layer, OPV devices exhibiting high transparency and a wide and high‐purity color gamut are obtained: blue (B), green (G), yellow‐green (YG), yellow (Y), orange (O), and red (R). The power conversion efficiencies (PCEs) of the G, YG, and Y color devices are greater than 8%(AM 1.5 G irradiation, 100 mW cm− 2) with maximum transmittances (TMAX) of greater than 14.5%. An optimized PCE of 8.2% was obtained for the YG OPV [CIE 1931 coordinates:(0.364, 0.542)], with a value of TMAX of 17.3%(at 561 nm). As far as it is known, this performance is the highest ever reported for a transparent colorful OPV. Such high transparency and desired transmitted colors, which …..Read More

Cheng-Ming Hsieh, Yung-Sheng Liao, Yan-Ru Lin, Chih-Ping Chen, Cheng-Min Tsai, Eric Wei-Guang Diau, Shih-Ching Chuang

We demonstrated that two Lewis bases–urea and thiourea–acted as efficient additives for CH3NH3 (MA) PbI3− xClx and MAPbI3 perovskite solar cells (PSCs) and observed a significant increase in PCE for the MAPbI3 devices in the presence of 1% urea with a remarkable PCE of 18.8% using an extremely low annealing temperature (85° C)...Read More

Nasima Khatun, Saurabh Tiwari, Jayanti Lal, Chuan-Ming Tseng, Shun Wei Liu, Sajal Biring, Somaditya Sen

Effect of uncompensated Ga-V co-doping on structural phase transition, grain growth process and optical properties of TiO2 is reported here. Inhibition of phase transition due to co-doping is confirmed by X-ray diffraction measurement. Activation energy of phase transition increases from 120KJ/mol (x= 0) to 140 KJ/mol (x= 0.046) due to Ga-V co-doping. In anatase phase, lattice constants increase by the effect of Ga3+ interstitials. This results in inhibition of phase transition. Anatase phase becomes stable up to~ 650 C in co-doped sample whereas for pure TiO2 phase transition starts in between 450-500 C. In anatase phase, strain increases due to co-doping which reduces crystallite size...Read More

Chun-Jen Shih, Chih-Chien Lee, Tzu-Hung Yeh, Sajal Biring, Kiran Kishore Kesavan, Nurul Ridho Al Amin, Ming-Hung Chen, Wei-Chieh Tang, Shun-Wei Liu, Ken-Tsung Wong

We report a new efficient exciplex-forming system consisting of a biscarbazole donor and a triazine-based acceptor. The new exciplex was characterized with a high photoluminescence quantum yield up to 68% and effective thermally activated delayed fluorescence behavior. The BCzPh:3P-T2T (2:1, 30 nm) blend was examined not only as an emitting layer (device D1) but also a reliable co-host of fluorescent and phosphorescent emitters for giving highly efficient exciplex-based organic light-emitting diodes (OLEDs) with a high maximum external quantum efficiency of 15.5 and 29.7% for devices doped with 1 wt % C545T (device D2) and 8 wt % Ir(ppy)2(acac) (device D4), respectively. More strikingly, a strongly enhanced lifetime (T75 = 16 927 min.) of the C545T-doped device was obtained. The transient electroluminescence measurement as well as capacitance–voltage and impedance–voltage correlations …..Read More

Tulika Srivastava, Gaurav Bajpai, Shun Wei Liu, Sajal Biring, Somaditya Sen

Effect of different wavelengths (350, 380, 390, 400, 450, 550 & 650 nm) of light on surface conductivity of sol-gel synthesized Zn 1− x Si x O material has been observed. Enhancement in conductivity at all wavelengths of light had been attributed to enhanced charge carrier concentration with silicon doping. Reduction in sensitivity for UV and visible light wavelength indicates reduction of surface defects and deep level traps with Si 4+ incorporation. Enhanced photo stability with Si 4+ doping makes it an appropriate material for transparent electrodes used in various display and electronic devices...Read More

Gaurav Bajpai, Tulika Srivastava, N Patra, Igamcha Moirangthem, SN Jha, D Bhattacharyya, Sk Riyajuddin, Kaushik Ghosh, Dharma R Basaula, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Substituting an ion of different size from that of the host element introduces lattice strain and defects. However, this mismatch may be significantly reduced by substituting an additional ion with a compensating size relative to the dopant. Such a double substitution might offer better solubility irrespective of the local distortions as well as the formation of defects in the valence states. Fe-substituted ZnO has been widely reported with conflicting results primarily arising from lack of chemical and structural homogeneity originating from preparation techniques, compositional fluctuations, and equivocal comprehension of actual solubility limits of the dopants. In this study, Ag ion has been incorporated in Fe-substituted ZnO to compensate the ionic size of Zn1−x[Fe0.8Ag0.2]xO (0 ≤ x ≤ 0.03125) by determining the solubility limit of the homogeneous material and their corresponding structural, mechanical, optical and …..Read More

Saurabh Tiwari, Gyanendra Rathore, N Patra, AK Yadav, Dibyendu Bhattacharya, SN Jha, CM Tseng, SW Liu, Sajal Biring, Somaditya Sen

Local and long range structure, optical and photoluminescence properties of sol-gel synthesized Ce1-xNixO2 nanostructures have been studied. The crystal structure, lattice strain and crystallite size have been analyzed. A decrease in lattice parameter may be attributed to substitution of Ce with smaller Ni ion. UV-Vis measurement is used for studying the effect of Ni substitution on bandgap and disorder. The bandgap decreases with Ni substitution and disorder increases. The PL spectra show five major peaks attributed to various defect states. The PL emission decreases with Ni substitution owing to increase in defects which acts as emission quenching centers. The lattice disorder and defects have been studied using Raman spectroscopy. Raman measurement shows that oxygen vacancies related defects are increasing with Ni substitution which causes changes in optical and PL properties. Local structure measurements show that Ni substitution leads to oxygen vacancies which does change host lattice structure notably. Ce4+ to Ce3+ conversion increases with Ni substitution...Read More

Mohd Nasir, Sunil Kumar, N Patra, D Bhattacharya, SN Jha, Dharma R Basaula, Subhash Bhatt, Mahmud Khan, Shun Wein Liu, Sajal Biring, Somaditya Sen

Rare earth Manganite Nickelite double perovskites are prepared by solgel assisted combustion route, where, R varies from La, Pr, Nd, Sm, Gd, Tb, Dy, Y, and Ho. The samples have been systematically investigated using powder xray diffraction, Raman spectroscopy, ultraviolet visible spectroscopy, magnetization, and synchrotron based xray absorption spectroscopy measurements. All compounds in the family crystallize in the monoclinic structure and the monoclinic distortion enhances with decreasing trivalent rare earth radii. The magnetic ordering temperature, Tc, decreases from 270 K for La to 80 K for Ho samples as the rare earth radii decrease from 0.116 nm for La to 0.102 nm in case of Ho. ..Read More

Gaurav Bajpai, Tulika Srivastava, N Patra, Igamcha Moirangthem, SN Jha, D Bhattacharyya, Sk Riyajuddin, Kaushik Ghosh, Dharma R Basaula, Mahmud Khan, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Correction for ‘Effect of ionic size compensation by Ag+ incorporation in homogeneous Fe-substituted ZnO: studies on structural, mechanical, optical, and magnetic properties’ by Gaurav Bajpai et al., RSC Adv., 2018, 8, 24355–24369...Read More

Tzu-Hung Yeh, Chih-Chien Lee, Chun-Jen Shih, Gautham Kumar, Sajal Biring, Shun-Wei Liu

We report a highly efficient transparent and inverted organic light-emitting diode (OLED) with a vacuum-deposited MoO 3 (5 nm)/Ag (12 nm)/WO 3 (40 nm)(MAW) multilayered electrode having a low sheet resistance of 4.2 Ω/sq, an average transmittance of 88% at a wavelength of 500–550 nm, and a smooth morphology with a root-mean-square roughness of 0.339 nm. The inverted phosphorescent OLED with MAW anode exhibits a total (sum of the bottom and top emissions) maximum power efficiency of 62.1 l m/W and an external quantum efficiency of 20.1%. In addition, the transparent device can achieve almost equal bottom-to-top emission ratio of 1: 1.1 and a total transmittance of> 80% in the visible-light range. The better device performance arises from the transparent MAW electrode acting as a capping layer to modulate the bottom/top emission direction and the optical properties of the device...Read More

Saurabh Tiwari, Nasima Khatun, Parasmani Rajput, Dibyendu Bhattacharya, SN Jha, Chuan-Ming Tseng, Shun-Wei Liu, Sajal Biring, Somaditya Sen

CeO2 has cubic fluorite structure which is modified due to oxygen content as well as external substituents. The oxidation state of Ce plays an important role in strain and related physical properties. Ce3+ being larger in size than the Ce4+ ion, one expects a change in band structure due to changes in bond length; substitution of Ce4+ by Co2+ in sol–gel prepared, homogeneous, single-phase Ce1−xCoxO2 (x ≤ 10) nanopowders. The lower valence states of Co2+ induces oxygen vacancies which transforms some Ce4+ to Ce3+. A careful study of oxygen vacancies, strain, bond length and related band structure changes, have been targeted in this study. The possibility of phonon participation in electronic transition has been discussed using Tauc plot. Ce3+ forms defect states, between valence and conduction bands. Lattice parameters decrease, but strain increases with substitution...Read More

Saurabh Tiwari, Nasima Khatun, Tulika Shrivastava, Sunil Kumar, Shun-Wei Liu, Sajal Biring, Somaditya Sen

CeO2 has a robust cubic fluorite face centered cubic (f.c.c.) structure. However, substitution in CeO2 can introduce lattice defects, tune optical properties and generate different functionalities. The oxidation state of a substituent triggers a Ce4+→Ce3+ transformation without destroying the structure but modifies the structure by generating defects. These structural changes should affect physical properties such as mechanical hardness along with electrical, optical and other properties. Mn substitution results in considerable changes in lattice parameters. Optical properties are affected. It is the valence state and ionic radius of the substituent which dominate the structural, vibrational and optoelectronic properties. Analysis reveals contraction of unit cell and increase in lattice strain affecting the hardness of the material. Microhardness studies show Indentation Size Effect with dominant plastic deformation...Read More

Abhyuday Paliwal, Satya Veer Singh, Anand Sharma, Anumol Sugathan, Shun-Wei Liu, Sajal Biring, Bhola N Pal

A rapid microwave-polyol technique is developed to grow bare-surface sub-10-nm lead sulfide (PbS) colloidal nanocrystals (NCs) of uniform size. Growth involves three distinct dynamical stages. PbS NCs homogeneously nucleate and undergo a fast growth process that spontaneously aggregates them into a continuous microstructure of PbS. Next, the interaction of low-power microwave irradiation with the NCs’ dipole moments along different crystallographic axes leads to the development of strain at the NCs’ grain boundaries, which ultimately causes dissociation of the aggregated microstructures into individual uniform-sized PbS NCs. The most distinctive feature of this growth technique is the bare nature and uniform size of the NCs produced. This gives the freedom to fabricate a highly packed NC thin film, which is essential for enhanced charge-transport properties. It simultaneously also precludes the need of …..Read More

Nasima Khatun, Saurabh Tiwari, Jayanti Lal, Chuan-Ming Tseng, Shun Wei Liu, Sajal Biring, Somaditya Sen

Uncompensated Ga-V co-doped TiO2 samples have been prepared by modified sol-gel process. Inhibition of phase transition due to co-doping is confirmed by X-ray diffraction measurement. Activation of phase transition increases from 120 kJ/mol (x = 0) to 240 kJ/mol (x = 0.046) due to Ga-V incorporation. In anatase phase, lattice constant increases by the effect of Ga3+ interstitials. This results in inhibition of phase transition. Anatase phase becomes stable up to ~ 650 °C in co-doped sample whereas for pure TiO2 phase transition starts in between 450 and 500 °C. High-resolution transmission electron microscope image shows particle size decreases in anatase phase due to co-doping. Increasing strain due to Ga-V incorporation results in reducing crystallite size. Brunauer–Emmett–Teller analysis shows that surface increases from 4.55 m2/g (pure TiO2) to 96.53 m2/g (x = 0.046) by Ga-V …..Read More

Publications 2017

Chun-Jen Shih, Chih-Chien Lee, Ying-Hao Chen, Sajal Biring, Gautham Kumar, Tzu-Hung Yeh, Somaditya Sen, Shun-Wei Liu, Ken-Tsung Wong

An exciplex forming co-host system is employed to achieve highly efficient organic light- emitting diode (OLED) with good electroluminescent lifetime. The exciplex is formed at the interfacial contact of a conventional star-shaped carbazole hole-transporting material, 4, 4', 4 “-tris (N-carbazolyl)-triphenylamine (TCTA) and a novel triazine electron-transporting material, 2, 4, 6-tris [3-(1H-pyrazol-1-yl) phenyl]-1, 3, 5-triazine (3P-T2T). The excellent combination of TCTA and 3P-T2T is applied as co-host of a common green … ...Read More

Yea-Fen Jang, Tzu-Chun Lin, Jhih-Yan Guo, Chien-Ming Fan Chiang, Ming-Lun Wu, Hsin-Yi Shen, Tsung-Cheng Chen, Zu-Po Yang, Ya-Ju Lee, Hai-Ching Su, Chih-Hao Chang, Shun-Wei Liu

Abstract Solid-state light-emitting electrochemical cells (LECs) show several advantages over conventional organic light-emitting devices (OLEDs) such as simple device structure compatible with solution processes, low operation voltage and capability of utilizing inert cathode metals. However, device performance of LECs must be improved, eg enhancing light extraction, to meet the requirements for practical applications. Among the optical modes trapped in LECs, light trapped in substrate mode is easier to be extracted, eg, by simply …..Read More

Ko-Wei Chen, Li-Yen Lin, Yi-Hua Li, Ya-Ze Li, Thanh Phuc Nguyen, Sajal Biring, Shun-Wei Liu, Ken-Tsung Wong

Abstract Four new molecules with acceptor-donor-acceptor (ADA) configuration where cyclopenta [2, 1-b: 3, 4-b′] dithiophene (CPDT) as the electron-donating core connecting to cyano (CN)-substituted 2, 1, 3-benzothiaidiazole (BT) as electron-withdrawing end groups are reported. With the same acceptor CN-BT, we found that CPDT can serve as a better donor as compared to that of dithieno [3, 2-b: 2′, 3′-d] silole (DTS) to give stronger intramolecular charge transfer (ICT) character and therefore better light harvesting ability …..Read More

Jun Lin, Yang Wang, Premkumar Gnanasekaran, Yu‐Cheng Chiang, Chun‐Chieh Yang, Chih‐Hao Chang, Shih‐Hung Liu, Gene‐Hsiang Lee, Pi‐Tai Chou, Yun Chi, Shun‐Wei Liu

Abstract Bis-tridentate Ir (III) metal complexes are expected to show great potential in organic light-emitting diode (OLED) applications due to the anticipated, superb chemical and photochemical stability. Unfortunately, their exploitation has long been hampered by lack of adequate methodology and with inferior synthetic yields. This hurdle can be overcome by design of the first homoleptic, bis-tridentate Ir (III) complex [Ir (pzpyph)(pz H pyph)](1), for which the abbreviation (pzpyph) H (or pz H pyph) stands for the parent 2 …..Read More

Yuan Jay Chang, Jung-Lien Hsu, Yi-Hua Li, Sajal Biring, Tzu-Hung Yeh, Jhih-Yan Guo, Shun-Wei Liu

Abstract Fabrication of vacuum deposited small molecules organic solar cell with open- circuit voltage (V oc) exceeding 1 V is crucial in advancing the applications of organic photovoltaics (OPVs). Here, a novel carbazole-based donor-π bridge-acceptor (D-π-A) of p- type material (F-series) in combination with fullerene derivative C 60 or C 70 as n-type material for bulk-heterojunction OPVs with the structure of ITO/MoO 3 (15 nm)/F-series donor: C 60 or C 70 (40 or 80 nm)/BCP (7 nm)/Ag (120 nm) have been proposed. The …..Read More

Sajal Biring, Ya-Ze Li, Chih-Chien Lee, Arvind Pan, Gautham Kumar, Shun-Wei Liu

Abstract Pentacene based organic field effect transistors with polyvinyl phenol gate dielectric are fabricated by controlling the dielectric surface energy and grain size of the first monolayer of pentacene. In this work, we introduce a novel approach to tune the surface energy of the polymer dielectric. This is performed by baking the polymer dielectric, polyvinyl phenol, at different vacuum conditions at 160° C before the deposition of pentacene layer. After the deposition of pentacene, these devices exhibit dramatic improvement of carrier …..Read More

Jhih-Yan Guo, Yi-Hua Li, Chih-Chien Lee, Sajal Biring, Shun-Wei Liu

In this work, a novel time-of-flight (TOF) measurement was carried out by employing an ultra- thin charge generation layer (CGL) of chloroboron subphthalocyanine and C 60, which shows a highly absorption coefficient at 532 nm from Nd: YAG laser. This implies that the proposed CGL region can facilitate in generating huge number of charge carriers, ie holes or electrons in organic device under the pumping wavelength. Moreover, such CGL-TOF would significantly reduce the sample thickness to~ 100 nm compared to standard TOF …..Read More

Gautham Kumar, Sajal Biring, Yi-Nan Lin, Shun-Wei Liu, Chih-Hao Chang

Abstract We investigated an efficient organic light-emitting diodes (OLEDs) using an ultra- thin silver (Ag) anode, whereas Ag was deposited on a roughened glass substrate by laser patterning method. The thin-film property of this roughened silver anode exhibited an optical transmittance of more than 65% in visible light at 532 nm and a low electrical sheet resistance of 3.2 Ω/sq, which is superior to standard indium-tin-oxide (ITO) glass. Therefore, we report an ITO-free, exciplex-forming phosphorescent OLED showing Lambertian …..Read More

Anand Sharma, Nitesh Chourasia, Anumol Sugathan, Yogesh Kumar, Satyabrata Jit, Shun-Wei Liu, Anshu Pandey, Sajal Biring, Bhola Nath Pal

Li5AlO4, a well-known material for solid state electrolyte application, has never been considered hitherto as a gate dielectric of metal oxide thin film transistor (TFT). Here we demonstrate the salient features of Li5AlO4 as a gate dielectric outperforming the conventional inorganic dielectrics used in TFT. The high dielectric constant (k) of this insulator has been achieved by utilizing the improved capacitance contributed by the mobile lithium ion (Li+) within the dielectric film. We have synthesized this dielectric by cost …..Read More

Chih-Chien Lee, Chun-Jen Shih, Gautham Kumar, Sajal Biring, Somaditya Sen, Shun-Wei Liu

We propose a DC sputtering process to fabricate an indium-tin oxide (ITO) electrode with nano-pinhole morphology for an efficient exciplex organic light-emitting device (OLED). The ITO thin-film of 80 nm thickness sputtered at room temperature shows an optical transmittance of over 86.5% in the range of visible light and an electrical sheet resistance of 75 ohm sq− 1. A layer of di-[4-(N, N-ditolyl-amino)-phenyl] cyclohexane (HATCN) is inserted into the device to improve the hole injection efficiency by reducing the injection barrier at …..Read More

Yuan-Chih Lo, Hao-Chun Ting, Ya-Ze Li, Yi-Hua Li, Shun-Wei Liu, Kuo-Wei Huang, Ken-Tsung Wong

The synthesis, structure, and properties of three new 5, 6, 11, 12-tetraarylindeno [1, 2-b] fluorenes are reported. The highly twisted conformations between an indeno [1, 2-b] fluorene core and peripheral aryl substitutions endow these indeno [1, 2-b] fluorene derivatives with good photostability for use as electron donors for vacuum-deposited photovoltaic devices. The optimized device based on a TAInF2 donor blended with C70 a..Read More

Nasima Khatun, Parasmani Rajput, Dibyendu Bhattacharya, SN Jha, Sajal Biring, Somaditya Sen

Abstract The anatase to rutile phase transition of TiO 2 which normally occurs at 750° C, is reduced to temperatures below 600° C by vanadium doping. The structural transformation is observed by a systematic study in the temperature range from 450° C to 750° C. The introduction of vanadium in rutile lattice is found to have impact on lattice parameters and particle size. This substitution also helps to reduce the bandgap of rutile TiO 2 to 1.76 eV from 3.04 eV upon 6 at% of vanadium doping. Vanadium induces additional donor level …..Read More

Mohd Nasir, AK Bera, SM Yusuf, DK Shukla, Sunil Kumar, DM Phase, Shun-Wei Liu, Sajal Biring, Somaditya Sen

Abstract: Among multifunctional double perovskite oxides, La2NiMnO6 has recently drawn significant attention due to its rich physics and potential for device applications. The relative variation in Ni: Mn ratio strongly influences the structural, magnetic and electric properties of La2NiMnO6. In the present study, La2Ni1. 5Mn0. 5O6 with Ni: Mn= 3: 1 ratio is synthesized using sol-gel method. Modifications of the above physical properties are discussed. Rietveld analysis of X-ray diffraction data shows that La2Ni1. 5Mn0. 5O6 samples belong to a …..Read More

Tulika Srivastava, Gaurav Bajpai, Gyanendra Rathore, Sajal Biring, Somaditya Sen

Abstract: UV sensing in pure ZnO is due to oxygen adsorption/desorption process from ZnO surface. Vanadium doping improves UV sensitivity of ZnO. Enhancement in UV sensitivity in doped ZnO is attributed to trapping and de-trapping of electrons at V4+ & V5+-related defect states. An extra electron in the V4+ state is excited under UV illumination while in absence of the same a trapping happens at the V5+ state. An insight to the mechanism is obtained by an analytic study of the response phenomenon...Read More

Tulika Srivastava, Gaurav Bajpai, Nidhi Tiwari, Dibyendu Bhattacharya, SN Jha, Sunil Kumar, Sajal Biring, Somaditya Sen

Vanadium incorporation in ZnO modifies the lattice structure. The valence state of V plays an important role, controlling the oxygen content and thereby dimensions of the lattice. Both V4+ and V5+ are more electropositive than Zn2+ and reduce oxygen vacancies, resulting in lattice expansion. However, the sizes of both V4+ and V5+ are smaller than Zn2+, thereby resulting in the lattice contraction. The internal competition of increasing oxygen content and reducing effective crystal radius decides the lattice expansion and contraction. This …..Read More

Tulika Srivastava, Aswin Sadanandan, Gaurav Bajpai, Saurabh Tiwari, Ruhul Amin, Mohd Nasir, Sunil Kumar, Parasharam M Shirage, Sajal Biring, Somaditya Sen

Abstract Si addition in ZnO lattice significantly improves electrical conductivity. The extra charge of Si 4+ ion (in comparison to Zn 2+) attracts more oxygen in the lattice and reduces oxygen vacancies. Reduction of oxygen vacancies (defects) reduces strain in the lattice. Transparency of visible light (< 3.0 eV) improves due to reduction of these defects in the wide bandgap (~ 3.3 eV: UV) of ZnO. Extra charge of Si 4+ enhances carrier density in the ZnO lattice. Improved carrier density, reduced strain facilitate transport of carriers and …..Read More

Arun Kumar Yadav, Parasmani Rajput, Ohud Alshammari, Mahmud Khan, Gautham Kumar, Sunil Kumar, Parasharam M Shirage, Sajal Biring, Somaditya Sen

Abstract Recently interest in finding magnetoelectric coupling in Fe substituted PbTiO 3 is observed. Synthesis of single phase PbTi (1− x) Fe (x) O 3 is a challenge which we report for 0≤ x≤ 0.5. PbTiO 3 is a strong ferroelectric. Fe substitution at the Ti site may lead to a potential magnetoelectric multiferroic material maintaining the non-centrosymmetric lattice distortion due to elongation of Ti-O octahedral in PbTiO 3 intact. The synthesis chemistry is a determining factor on the pure phase. Valence state, size and coordination of substituting …..Read More

Arun Kumar Yadav, Anita Verma, Sunil Kumar, V Raghavendra Reddy, Parasharam M Shirage, Sajal Biring, Somaditya Sen

Abstract: PbTiO3 has the highest tetragonal distortion (c/a= 1.064) and highest spontaneous polarization among perovskite titanates. But, it is hazardous and hence one needs to reduce Pb content by substituting or reducing Pb content for use in applications. Pb (1-x)(K0. 5Sm0. 5) xTiO3 (0&x&0. 5) perovskite powders were synthesized by sol-gel process, where Pb2+ was replaced by a combination of K+ 10.5 Sm+ 30.5 (equivalent charge and comparable ionic radius) providing an excellent substitution model to study changes in structural and …..Read More

Saurabh Tiwari, Gaurav Bajpai, Tulika Srivastava, Srashti Viswakarma, Parasharam Shirage, Somaditya Sen, Sajal Biring

Abstract CeO 2, a strong cubic fluorite structured ceramic, with well-defined optical and mechanical properties may be modified by proper substitution. Ni substitution in Ce 1− x Ni x O 2 (0≤ x≤ 0.08) nanoparticles, hints at strain generation in the lattice bringing in changes in structural properties. The strain introduces changes in the electronic, optical and mechanical properties. The origin of strain is discussed using structural, optoelectronic, vibrational and mechanical studies discussing the elastic and plastic behavior of the …..Read More

SC Chuang CM Hsieh, YL Yu, CP Chen

Organic–inorganic lead halide perovskite solar cells (PSCs) offer a promising low-cost manufactural solar technology as they are compatible with large-scale and low-temperature (< 100° C) solution processes. Through the optimization of perovskite active layer and phenyl-C61-butyric acid methyl ester (PC61BM) layer thickness, the normal cells showed 9.7% power conversion efficiency (PCE). Compared with the corresponding normal devices, we observed an improvement in PCE from 9.7% to 11.3% and 10.2% for the devices …..Read More

CP Chen YY Yu, YJ Ting, CL Chung, TW Tsai

Abstract In this study, chemical treatment (CT; oxidation–reduction method) and physical treatment (HP; hot-pressing methods) were applied to improve the performance of silver nanowire (AgNW)-derived electrodes on a glass or flexible polyethylene terephthalate (PET) substrate. The four-point probe method, UV-Vis spectroscopy and scanning electron microscopy (SEM) were used to measure the properties of AgNW electrodes and compare them with those of indium tin oxide (ITO) electrodes for exploring the possibility of using …..Read More

Yu-Lung Weng, Yi-Chan Li, Chih-Ping Chen, Yuan Jay Chang

Abstract Six novel small molecules containing phenothiazine as the core moiety of p-type materials were synthesized in combination with PC 61 BM or PC 71 BM as n-type materials for bulk heterojunction organic photovoltaic (OPV) cells. Phenothiazine was used as donor building blocks to construct acceptor–donor–acceptor (A–D–A) and A–D–D–A small molecule. We investigated the relationship between the molecular structures, optoelectronic and thermal properties, and their blend film morphologies for OPV applications. We …..Read More

Ying-Chieh Chao, Shih-Chieh Yeh, Hsiang-Lin Hsu, Bing-Huang Jiang, Kuo-Hua Sun, Chin-Ti Chen, Chih-Ping Chen, Ru-Jong Jeng

Abstract In this study, we synthesized two emeraldicene (EMD)-based conjugated polymers, PBTEMD and PFEMD, through polymerization of 4, 7-di (thien-2-yl) benzo [c][1, 2, 5] thiadiazole and 9, 9-bis (2-ethylhexyl)-9H-fluorene, respectively. We then blended these EMD-derived polymers (as electron-donating materials) with [6, 6]-phenyl-C 71-butyric acid methyl ester (PC 71 BM) in the active layers of polymer solar cells (PSCs) and investigate their optoelectronic properties and related photovoltaic performance. To best of our …..Read More

Yang-Yen Yu, Tzung-Wei Tsai, Chun-Chen Yang, Chih-Ping Chen

Most efficient organic photovoltaic (OPV) devices are fabricated using halogenated solvents, which are hazardous and environmentally unfriendly. From an industrial perspective, green solvents are necessary for the roll-to-roll production of OPV modules. In this study, we fabricated nonfullerene (NF) OPV devices that are based on the blend films of PTB7-Th and 3, 9-bis (2-methylene-(3-(1, 1-dicyanomethylene)-indanone)-5, 5, 11, 11-tetrakis (4-hexylphenyl)-dithieno [2, 3-d: 2′, 3′-d′]-s-indaceno [1, 2-b: 5, 6-b′]-dithiophene (ITIC …..Read More

Yang-Yen Yu, Chien-Hsun Chen, Chu-Chen Chueh, Chun-Ying Chiang, Jang-Hsing Hsieh, Chih-Ping Chen, Wen-Chang Chen

In this study, a new hybrid electrode featuring a high gauge factor of> 30, decent stretchability (100% of the original conductivity can be retained after 50 cycles of stretching under a 20% strain without prestrain treatment), high transmittance (> 70%) across 400–900 nm, and a good sheet resistance (< 50 Ω sq–1) was successfully exploited. These superior properties were revealed to originate from the reversible phase separation endowed by the nanogranular-like morphology formed in Ag. Owing to such discrete nanomorphology, the …..Read More

Ching-Chih Chang, Bing-Huang Jiang, Yi-Chan Li, Chih-Ping Chen, Chien-Hong Cheng

Abstract Varying the structures of conjugated side chains can be an efficient approach toward tailoring the optoelectronic properties of conjugated polymers. In this study, we synthesized four indacenodithiophene (IDT)-based side chain conjugated donor–acceptor alternating polymers. We introduced four different acceptor units (difluorobenzothiadizole: PIDTHT-FBT; difluoroquinoxaline: PIDTHT-QF; dicyanoquinoxaline: PIDTHT-QCN; diketopyrrolopyrrole: PIDTHT-DPP) to study the effects of the conjugated side chains on …..Read More

Chien-Tien Chen, Fang-Yuan Tsai, Chun-Ying Chiang, Chih-Ping Chen

A spiro core appended with trithiophene arms and α-cyanoacrylate end groups was used for the first time in bulk heterojunction solar cell applications. The resulting device performance was evaluated by its blending with PC61BM, leading to a short-circuit current density (J sc) of 3.55 mA cm–2 which was 2.4 and 6.6 times better than those of the open form and nonspiro core analogs. The 1, 8-diiodooctane solvent additive suppressed its microcrystalline self-aggregation, leading to a well-defined blend film morphology with …..Read More

Chih-Ping Chen, Chun-Ying Chiang, Yang-Yen Yu, Yu-Sheng Hsiao, Wen-Chang Chen

Abstract Electronic skins and smart textiles are emerging applications integrating wearable displays, smart sensing systems, health-care monitors, and stretchable power systems. Although various deformable optoelectronic devices have been demonstrated, high-performance stretchable photovoltaic (PV) devices remain a significant challenge in device engineering and materials optimization. In this paper, we demonstrate how a ubiquitous material—3 M™ tape—can be used as a transparent substrate for highly efficient …..Read More

Jong‐Hong Lu, Yi‐Hung Lin, Bing‐Huang Jiang, Chun‐Hung Yeh, Jui‐Chih Kao, Chih‐Ping Chen

Abstract High-performance colored aesthetic semitransparent organic photovoltaics (OPVs) featuring a silver/indium tin oxide/silver (Ag/ITO/Ag) microcavity structure are prepared. By precisely controlling the thickness of the ITO layer, OPV devices exhibiting high transparency and a wide and high-purity color gamut are obtained: blue (B), green (G), yellow-green (YG), yellow (Y), orange (O), and red (R). The power conversion efficiencies (PCEs) of the G, YG, and Y color devices are greater than 8%(AM 1.5 G irradiation, 100 …..Read More

Bing-Huang Jiang, Ya-Juan Peng, Chih-Ping Chen

In this study, we have found that interfacial layers (IFLs) based on Jeffamines (industrial polyetheramine derivatives) can improve the performance of organic photovoltaics (OPVs). We evaluated four different Jeffamines (average molecular weight: 2000 g mol− 1)—M2005, M2070, D2000, and ED2003—having either a monoamine or diamine structure and various ratios of propylene oxide (PO) and ethylene oxide (EO) for their suitability as IF materials for OPV applications. The presence of the Jeffamine altered the work function of ZnO and …..Read More

Hoang Chinh Nguyen, Shih-Hsiang Liang, Thien Thanh Doan, Chia-Hung Su, Pei-Cheng Yang

Abstract Black soldier fly larvae (BSFL), oleaginous insects, can assimilate several organic wastes for fat accumulation, thus serving as a promising feedstock for biodiesel production. In this study, the transesterification of BSFL fat and methanol was catalyzed using lipases to produce environmentally friendly biodiesel. Different commercial lipases were evaluated for their catalytic activity in the reaction. Among the examined biocatalysts, Novozym 435, an immobilized enzyme, showed the highest activity level. Response surface methodology was subsequently used to optimize the lipase-catalyzed reaction and to develop a reliable empirical model for prediction. A maximum biodiesel yield of 96.18% was obtained at a temperature of 26 C, methanol: fat molar ratio of 6.33, enzyme loading of 20%, and reaction time of 9.48 h. Under the optimal reaction conditions and enzyme regeneration process …..Read More

Hoang Chinh Nguyen, Szu-Pei Wu, Chia-Hung Su, Tzann-Shun Hwang

Résumé Description du sujet. Les phosphatases alcalines (APases) sont fréquemment employées comme marqueurs non radioactifs pour la détection spécifique de protéines ou d'ADN cibles en médecine clinique et en biologie moléculaire. Toutefois, leur application en biotechnologie industrielle nécessite une bonne stabilité tant thermique que de conservation. Nos recherches préliminaires ont montré que l'APase de Thermus sp. NTU- 237 (TsAPase) est thermostable et présente une haute activité. Il est donc intéressant d'établir les conditions optimales de son emploi. Objectifs. Caractériser l'APase de la souche thermophile Thermus sp. NTU-237 et évaluer ses potentialités d'application. Méthode. Le gène de l'APase de Thermus sp. NTU-237 a été cloné pour être exprimé dans Escherichia coli. Cela a permis l'étude des effets sur l'activité enzymatique TsAPase, de la …..Read More

Fu Ming Wang, Sylvia Ayu Pradanawati, Nan-Hung Yeh, Shih-Chang Chang, Ya-Tang Yang, Shih-Han Huang, Ping-Ling Lin, Jyh-Fu Lee, Hwo-Shuenn Sheu, Meng-Lin Lu, Chung-Kai Chang, Alagar Ramar, Chia-Hung Su

Electric vehicles (EVs) are poised to dominate the next generation of transportation, but meeting the power requirements of EVs with lithium ion batteries is challenging because electrolytes containing LiPF6 and carbonates do not perform well at high temperatures and voltages. However, lithium benzimidazole salt is a promising electrolyte additive that can stabilize LiPF6 through a Lewis acid–base reaction. The imidazole ring is not eligible for high-voltage applications owing to its resonance structure, but in this research, electron- withdrawing (− CF3) and electron-donating (− CH3) substitutions on imidazole rings were investigated. According to the calculation results, the CF3 substitution facilitates a high electron cloud density on imidazole ring structures to resist the electron releases from bezimidazole in oxidation reactions. In addition, through CF3 substitution, electrons are …..Read More

Chia-Hung Su, Govindarajan Venkat Kumar, Shritama Adhikary, Palaniyandi Velusamy, Kannaiyan Pandian, Periasamy Anbu

Abstract There is a vital need for the production of clean, hygienic, and antibacterial textile fabric for use as hospital clothing, surgical scrubs and linens to protect against nosocomial pathogens. In the present study, cotton fabrics were treated with sodium alginate-capped silver nanoparticles and were tested for antibacterial activity against nosocomial pathogens. The sodium alginate-capped silver nanoparticles were synthesized under various experimental conditions by using varying sodium alginate concentrations (0.5–2%), volumes of reducing agent aniline (50, 100, 150 μL), and durations of heat treatment (30–240 s). The synthesized nanoparticles were characterized using ultraviolet-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Furthermore, the antibacterial efficacy of sodium alginate-capped silver nanoparticles …..Read More

Chia Hung Su, Palaniyandi Velusamy, Govindarajan Venkat Kumar, Shritama Adhikary, Kannaiyan Pandian, Periyasamy Anbu

Abstract In the present study, a simple method to impregnate silver nanoparticles (AgNPs) into carboxymethyl cellulose (CMC) and sodium alginate (SA) is reported for the first time. Single step synthesis of carboxymethyl cellulose (CMC) and sodium alginate (SA) biopolymer protected silver nanoparticles (AgNPs) using aniline as a reducing agent under reflux conditions was investigated. The synthesized nanoparticles were characterized by UV– Vis spectrophotometry, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). The FESEM results of CMC@ AgNPs and SA@ AgNPs showed the formation of spherical nanoparticles sized 30– 60 nm. Testing of the antibiofilm efficacy of the polymer protected AgNPs against different bacterial strains such as Klebsiella pneumoniae MTCC 4032 and Streptococcus …..Read More

Thi My Huong Dinh, Chia Hung Su

Tóm tắt: Nhiên liệu sinh học là một nguồn nhiên liệu tái tạo, được sản xuất thông qua quá trình chuyển ester hóa dầu thực vật, mỡ động vật, hay quá trình este hóa axit béo và ancol mạch ngắn (metanol, etanol, propanol and butanol) với sự có mặt của các loại xúc tác axit, bazo vô cơ hoặc enzyme. Nghiên cứu ảnh hưởng của các điều kiện tiến hành quá trình este hóa axit béo với methanol để sản xuất dầu sinh học bằng chất xúc tác là enzyme lỏng với chất siêu hấp thụ (SAP) nhằm mục đích xác định các giá trị tối ưu của các yếu tố ảnh hưởng đến quá trình phản ứng bao gồm nhiệt độ, tỉ lệ mol chất phản ứng, hàm lượng chất xúc tác và SAP. Kết quả nghiên cứu cho thấy rằng ở nhiệt độ 45ºC, tỉ lệ mol giữa axit béo và methanol là 1: 3, hàm lượng xúc tác và SAP đã sử dụng là 10% khối lượng acid thì hiệu suất phản ứng đạt giá trị cao nhất gần 90% sau 6 giờ phản ứng...Read More

Hoang Chinh Nguyen, Szu-Pei Wu, Chia-Hung Su, Tzann-Shun Hwang

(1) Ton Duc Thang University. Faculty of Applied Sciences. 19 Nguyen Huu Tho St. Tan Phong Ward. Dist. 7. Ho Chi Minh City 700000 (Vietnam). (2) Yuanpei University. Department of Biotechnology and Pharmaceutical Technology. 306 Yuanpei St. Xiangshan, Hsinchu City 30015 (Taiwan). (3) Ming Chi University of Technology. Graduate School of Biochemical Engineering. 84 Gungjuan Rd. Taishan, Taipei 24301 (Taiwan). Email: chsu@mail.mcut.edu.tw (4) Chinese Culture University. Graduate Institute of Biotechnology. 55 Hwa-Kang Rd. Yang-Ming-Shan. Taipei 11114 (Taiwan). E-mail: hzx@faculty.pccu.edu.tw … Description of the subject. Alkaline phosphatases (APases) are commonly used as nonradioactive markers for detecting specific proteins or DNA targets in clinical medicine and molecular biology. However, their applications in the biotechnology industry require thermostability and storage stability. Our preliminary study revealed that …..Read More

Cheng-Shane Chu, Zhi-Ren Su

This paper presents a ratiometric optical broad range pH sensor that comprises an optical fiber coated at one end with CdSe/ZnS quantum dots (QDs) and Oxazine 170 perchlorate (O170) embedded in ethyl cellulose (EC) matrix. The feasibility of coating an optical fiber with the sensing film to fabricate a ratiometric fiber optic broad range pH sensor is investigated. Using an LED with a central wavelength 405 nm as an excitation light source, the CdSe/ZnS QDs shows that the fluorescence intensity at 575 nm decreases with increasing pH and O170 shows the fluorescence intensity at 655 nm increases with increasing pH. The ratio of fluorescence intensities at 575 nm and 655 nm has a linear relationship with pH value in the 1.6-13.2 range. The ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the …..Read More

Cheng-Shane Chu, Yen-Fu Chen

A simple, low cost technique to fabricate a ratiometric optical fiber ammonia (NH 3) sensor has been presented. The ratiometric optical fiber ammonia sensor was based on the ammonia induced absorbance change of sensing material Oxazine 170 perchlorate (O170) in ethyl cellulose (EC) with the luminescence intensity of 7-amino-4-trifluoromethyl coumarin (AFC). The observed luminescence intensity from AFC at 487 nm decreased with increasing the ammonia concentration. The sensitivity of optical ammonia sensor is quantified in terms of the ratio I 0/I 100, where I 0 and I 100 represent the detected luminescence intensities in nitrogen and 1000 ppm ammonia concentration, respectively. The experimental result shows that the sensitivity of the ratiometric optical fiber ammonia sensor is estimated to be 1.44. The sensitive optical ammonia sensor based on fluorescence intensity changes of …..Read More

Cheng-Shane Chu, Meng-Wei Hsieh

A new optical carbon dioxide sensor based on the colormetric change of pH indicator a- naphtholphthalein with the internal reference fluorescent CIS/ZnS quantum dots (QDs) was developed. The luminescence intensity of CIS/ZnS QDs increased with increasing carbon dioxide concentration. The sensing films consisting of a-naphtholphthalein in polyIBM and CIS/ZnS QDs in polystyrene layer. The sensitivity of optical carbon dioxide sensor is quantified in terms of the ration I 100/I 0, where I 100 and I 0 represent the detected luminescence intensities in pure carbon dioxide and pure nitrogen environments, respectively. The experimental result reveals that the new optical carbon dioxide sensor has sensitivity of I 100/I 0= 13.4...Read More

Cheng-Shane Chu, Jhih-Jheng Syu

An optical sensor for the dual sensing of oxygen (O_2) and carbon dioxide (CO_2) based on sensing films coated on filter paper is proposed. Ethyl cellulose (EC) doped with platinum (II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) and 7-amino-4-trifluoromethyl coumarin serve as the oxygen sensing material and reference blue emission dye for the pH indicator, respectively. The CO_2 sensing layer includes the pH-sensitive fluorescent indicator 1-hydroxy-3, 6, 8-pyrenetrisulfonic acid trisodium salt immobilized within the EC. The O_2-and CO_2-sensitive materials can both be excited with a 405 nm LED, and the two emission wavelengths can be detected separately. The experimental result reveals that the optical O_2 and CO_2 sensors have sensitivities of I_N_2/I_100% O_2= 22.8 and I_N_2/I_100% CO_2= 3.6, respectively. The response times of the optical O_2 sensor …..Read More

Ming-Hung Chen

Abstract This paper is concerned with the design and implementation of the closed-loop controller with current sensors for brushless DC motor drives to yield good speed regulation, low current harmonic and stable output speed. The design of the controller is conducted by digitizing the mathematical model of brushless DC motors. The regulation and limitation of control parameters are also studied. The saliency of brushless DC motor yields larger quadrature-axis inductance than that of the direct-axis. This results in reluctance torque accordingly. By appropriately adjusting the direct-axis current, the reluctance torque can be controlled to achieve high-efficiency operation. The proposed control strategy will not only yield optimal efficiency but also result in the immunity of performance to the variation of machine parameters. A predicted current estimator is proposed to function under …..Read More

Hung-Ing Chen, Jui-Ju Hsiao, Chia-Hui Fang, Joe-Air Jiang, Jen-Cheng Wang, Ya-Fen Wu, Tzer-En Nee

Abstract The characteristics of the photocarrier transfer process in ZnO nanostructures fabricated on silicon substrates by the hydrothermal method are studied using temperature- dependent photoluminescence (PL) measurements. The luminescence shows distinct features arising from the dynamics of the excited carriers which occur as a consequence of the different size distributions of the ZnO nanostructures. It is found that the temperature- dependent photoluminescence phenomena can be attributed to the carrier-thermalization processes that occur in the ZnO nanostructures. The photogenerated carrier redistribution leads to a blueshift in the emission energy of the radiative transitions in the ZnO nanostructures. The random configuration of the photogenerated carriers in the ZnO nanostructures can be qualitatively understood in terms of the transition enthalpy and the …..Read More

Yi Chen, Wei-You Chen, Hung-Pin Hsu, Jiunn-Chyi Lee, Ya-Fen Wu

Abstract In this work, the hydrothermally grown ZnO nanostructures were successfully prepared on indium tin oxide glass using different aqueous solution molarities. The effect of solution molarity on the structual and optical properties of ZnO nanostructures were studied by X-ray diffraction and temperature-dependent photoluminescence (PL) measurements. The PL intensity ratio of the ultraviolet emission to the visible emission is also calculated. It is found that the crystal quality and the optical properties are improved by raising the solution molarity, but too higher solution molarity should lead to the disorder of ZnO structures, and deteriorate the crystal quality...Read More

Ya-Fen Wu, Jiunn-Chyi Lee

Abstract: We introduced multiquantum-barrier (MQB) nanostructures into the barrier layers of InGaN/GaN multiquantum-well (MQW) heterostructures to improve the operation characteristics of the light-emitting devices. The electroluminescence (EL) spectra were examined over a broad range of temperatures for the samples. We observed inhibited carrier leakage for the sample with the MQB nanostructures. Greater inhomogeneity of nanocrystallite size and a stronger localization effect were also observed for the sample. To interpret this phenomenon, high-resolution X-ray diffraction curves were measured and analyzed using the Warren–Averbach model. External quantum efficiency as a function of temperature was also evaluated. The calculation results correspond with the inference the EL measurements provided. We determined that the performance of the light-emitting …..Read More

Bing-Yuh Lu, Ming-Kwen Tsai, Jhen-Chen Wang, Meng-Lun Hsueh, Huey-Dong Wu, Jin-Shin Lai, Ya-Fen Wu, Tzer-En Nee

Abstract: The sound of the siren of the ambulance is for the safety of the road transportation, but interferes the auscultation of the lung and heart sounds. The system implementation is included by (1) ACER Aspire 17 notebook as a server in right side;(2) HwaWei Amazing A6 smart mobile as a hot point in the middle; and (3) ACER Aspire 5 notebook as a client which the settings include IP address of host computer, and client, read and, write privileges of the data sockets, and running of NI data socket manager, and data socket server. Therefore, the parameters in the real-time DAS are verified as the better ones to prepare for the services on the ambulance...Read More

Ya Fen Wu, Jiunn Chyi Lee

Quaternary AlInGaN/AlInGaN multiquantum-well (MQW) structures were grown by metal- organic vapour-phase epitaxy (MOVPE). The influence of QW pairs and QW barrier width on the optical properties of the samples is investigated by means of temperature and incident- power dependent photoluminescence (PL) measurements. The PL emission peaks redshift and the PL peak intensities increase as the number of QW pairs increases. On the other side, a blueshift of the PL peak energy and reduction of the PL peak intensity are observed for the sample with thinner barrier width. These results are explained by carrier localization effect. The S-shaped temperature-dependence of the PL peak energies indicates the existence of localized states induced by the potential fluctuations. The estimated degree of localization effect is found to be enhanced for the sample with more QW pairs and thicker …..Read More