Browsing by Author "Chen, Wen-Chang"

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Cesium carbonate as a functional interlayer for polymer photovoltaic devices
(2008-05-15)
Chen, Fang-Chung
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Wu, Jyh-Lih
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Yang, Sidney S.
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Hsieh, Kuo-Huang
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Chen, Wen-Chang
The device characteristics of polymer solar cells with cesium carbonate (Cs(2)CO(3)) as an electron-injection interlayer have been investigated. It is found that the insertion of Cs(2)CO(3) at the cathode interface improves the device power conversion efficiency from 2.3% to 3.1%. In order to further understand the mechanism, the interfacial interaction between the active organic layer and the cathode was studied by x-ray photoemission spectroscopy (XPS). The results of XPS measurement indicate the fact that a portion of electrons transfer from the interlayer into the organic layer, resulting in n-type doping. The n-doping effect enhances the efficiency of electron injection and collection. Further, the maximum open-circuit voltage (V(oc)) was determined from its temperature dependence. For the device with Cs(2)CO(3), the maximum V(oc) is extremely close to the corresponding value of the energy difference between the highest occupied molecular orbital of the electron donor and the lowest unoccupied molecular orbital of the electron acceptor, suggesting a better Ohmic contact. All evidences indicated that Cs(2)CO(3) is a promising candidate as an interlayer to improve the device performance. (C) 2008 American Institute of Physics.
Electrospun Fibers as a Solid-State Real-Time Zinc Ion Sensor with High Sensitivity and Cell Medium Compatibility
(2013-03-25)
Syu, Jia-Hao
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Cheng, Yi-Kai
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Hong, Wun-Yan
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Wang, Hsing-Ping
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Lin, Yu-Chao
meso-2,6-Dichlorophenyltripyrrinone (TPN-Cl2), a probe molecule for zinc II ions, is dispersed in a polymer host. The red fluorescence peak at 620 nm appears when the molecule forms a complex with zinc at its center. TPN-Cl2 has a high selectivity for zinc II and tolerates many common metal ions present in the human body. The probe molecules are blended with a hydrogel polymer, poly(2-hydroxyethyl methacrylate) (poly HEMA), with 30 wt% dimethylformamide (DMF). The fiber structure with 1 m diameter is made by electrospinning in DMF solution of the probe and poly HEMA mixture. The fibrous film detects zinc ions with concentrations as low as 106 M in real-time both in water and in the commonly used cell culture liquid media Dulbecco's modified Eagle medium (DMEM) and fetal bovine serum (FBS), which contain many metal ions and proteins. The time-resolution is 5 min for 106 M and 1 min for 105 M. This sensitivity and response speed satisfy the requirements for non-invasive biomedical studies.
Flexible Polymer Photovoltaic Devices Prepared With Inverted Structures on Metal Foils
(2009-07-01)
Chen, Fang-Chung
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Wu, Jyh-Lih
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Lee, Chia-Ling
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Huang, Wen-Che
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Chen, Huang-Ming Philips
We have prepared top-illuminated organic photovoltaic devices on stainless-steel substrates, using molybdenum trioxide/indium tin oxide as the transparent top electrode. Incorporating an Al counter electrode grid having a shadow fraction of 10% effectively reduced the device resistance, thereby enhancing the power conversion efficiency to ca. 3%. This device exhibited superior mechanical flexibility. The inverted device architecture eliminated the need to use low-work-function metals, which are air sensitive and easily oxidized, thereby improving the air stability of the flexible devices.
Infrared proximity sensor using organic light-emitting diode with quantum dots converter
(2012-11-01)
Chen, En-Chen
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Yeh, Han-Cheng
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Chao, Yu-Chiang
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Meng, Hsin-Fei
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Zan, Hsiao-Wen
An efficient visible-to-infrared conversion film is made by blending CdTe quantum dots (CdTe QDs) of 12 nm diameter in a polyvinylpyrrolidone 360 (PVP 360) polymer matrix cast by water solution. The solid-state photoluminescence quantum efficiency exceeds 10% with emission peak at 810 nm. Strong 810 emission is obtained by combining the quantum dot film and a green polyfluorene light-emitting diode. Color filter is used to remove residual light below 780 nm to make it entirely invisible. Infrared photo-detector is made by blending poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PBDOTTP) with band-gap 1.2 eV and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The pixel contains one PD surrounded by four PLED on its four sides. The active areas of the five devices are all I cm by 1 cm and they are on the same plane. Infrared proximity sensor with photo-current over 300 nA at 10 cm object distance is achieved by detecting the reflected infrared signal. (C) 2012 Elsevier B.V. All rights reserved.
Integrated semiconductor optoelectronic devices for real-time and indicator-free detection of aqueous nitric oxide
(2011-01-01)
Wang, Shin-Ping
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Cheng, Yi-Kai
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Chao, Yu-Chiang
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Zan, Hsiao-Wen
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Chang, Gao-Fong
Sensing films specific to nitric oxide and zinc were fabricated by embedding respectively indicator 1,2-diaminoanthraquinone (DAQ) and 11,16-Bis(phenyl)-6,6,21,21-tetramethyl-m-benzi-6,21-porphodimethene (BPDM-H) in hydrogel host poly(2-hydroxyethyl methacrylate). The sensing film contains DAQ, which responses to nitric oxide, shows stability in acid environment. The sensing film contains BPDM-H responses to zinc. The electrospinning technique was also utilized to fabricate the fibrous film.
New Thiophene-Phenylene-Thiophene Acceptor Random Conjugated Copolymers for Optoelectronic Applications
(2010-06-01)
Tsai, Jung-Hsun
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Chueh, Chu-Chen
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Chen, Wen-Chang
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Yu, Chao-Ying
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Hwang, Gue-Wuu
New low band gap thiophene-phenylene-thiophene (TPT)-based donor-acceptor-donor random copolymers were synthesized for optoelectronic device applications by a palladium-catalyzed Stille coupling reaction under microwave heating. The acceptors included 2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,8-bis[5'-bromo-dithien-2-yl-quinoxalines] (DTQ) and 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-ethyl-hexyl)-pyrrolo[3,4-c]-pyrrole-1,4-dione (DPP). The prepared random copolymers were named as PTPTDTQ(0.55), PTPTDTQ(0.34)DPP(0.14), and PTPTDTQ(0.26)DPP(0.34) depending on the copolymer ratio. The optical band gaps (Er) of PTPTDTQ(0.55), PTPTDTQ(0.34)DPP(0.14), and PTPTDTQ(0.26)DPP(0.34) were 1.74, 1.56, and 1.48 eV, respectively. The hole mobility obtained from the field-effect transistor devices prepared from PTPTDTQ(0.55), PTPTDTQ(0.34)DPP(0.14), and PTPTDTQ(0.26)DPP(0.34) were 2.2 x 10(-3), 2.4 x 10(-3), and 4.7 x 10(-3) cm(2) V s(-1), respectively, with the on-off ratios of 4.0 x 10(4), 4.0 x 10(4), and 5.3 x 10(4). It suggested that the significant intramolecular charge transfer between the TPT and acceptor led to the band gap reduction and hole mobility enhancement. Polymer solar cells of these TPT-based copolymers blended with 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-71 (PC(71) BM) under illumination of AM 1.5G (100 mW cm(-2)) solar simulator exhibited a power conversion efficiency (PCE) as high as 3.71%. Besides, the near-infrared photodetector device prepared from PTPTDTQ(0.26)DPP(0.34) showed a high external quantum efficiency exceeding 32% at 700 nm (under -3 V bias) and fast-speed response. This study suggests that the prepared TPT-based donor-acceptor random copolymers exhibited promising and versatile applications on optoelectronic devices. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2351-2360, 2010
Non-fluorinated superamphiphobic surfaces through sol-gel processing of methyltriethoxysilane and tetraethoxysilane
(2009-03-15)
Sheen, Yuung-Ching
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Chang, Wei-Hsuan
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Chen, Wen-Chang
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Chang, Yih-Her
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Huang, Yuan-Chang
In this study, a simple approach was developed to fabricate an extremely superamphiphobic coating material by the tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) sol-gel derived materials. TEOS and MTES derived moieties were designed for a physical roughness and hydrophobic surface characteristic, respectively. The (29)Si solid-state NMR and ESCA analysis showed the coated silica composition was similar to the feeding ratios of TEOS/MTES. The surface structure characterized from SEM and TEM suggested the nanoparticle-based silica surface was observed at a high TEOS/MTES content but changed to a relatively smooth surface at a low TEOS content. The contact angles of water and CH(2)I(2) on the pure TEOS derived coated surface were both 0 degrees due to the hydrophilic Si-OH group. As the MTES composition increased to 25 mol% (T5M3), the coated surface had the contact angles of 149.8 degrees and 133.1 degrees for water and CH(2)I(2), respectively. It revealed that the T5M3-coated surface exhibited both super-hydrophobicity and super-oleophobicity, i.e., superamphiphobicity. Also, it had a relatively low-surface energy (1.38 mJ m(-2)) considerably lower than that of the F-silane-coated surface with 39.3 mJ m(-2). As the MTES composition increased further, both contact angles of water and CH(2)I(2) decreased. Especially, they decreased dramatically at the MTES feeding composition higher than 75 mol%, due to the much less rough surface at a higher MTES composition. The present study suggests that superamphiphobic surface could be achieved by non-fluorinated sol-gel derived silica materials. (C) 2008 Published by Elsevier B.V.
Polymer infrared photo-detector with high sensitivity up to 1100 nm
(2011-08-01)
Chen, En-Chen
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Tseng, Shin-Rong
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Chao, Yu-Chiang
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Meng, Hsin-Fei
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Wang, Chih-Feng
We reported a low band-gap conjugated polymer, poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,7-di(thiophen-2-yl)thienol[3,4-b]pyrazine] (PDTTP), was studied for the near infrared (NIR) photo-detector application. PDTTP shows intense absorption in NIR wavelength (to 1000 nm) and the estimated optical and electrochemical band-gaps of PDTTP are quite small around 1.15 eV and 1.08 eV, respectively. The low band-gap and the extended long wavelength absorption originates from the introduction of alternating TP units when its parent polythieno[3,4-b]pyrazine shows excellent narrow band-gap properties. Therefore, the relatively low band-gap and intense absorption in long wavelength of PDTTP make itself a promising candidate for near-infrared photo-detector. The hole mobility of the PDTTP measured from the bottom contact field effect transistor is around 1.40 x 10(-3) cm(2)/V s with a on/off ratio of 2100. The photo-detector based on bulk hetero-junction PDTTP and (6,6)-phenyl-C61-butyric acid methyl ester blend (PCBM) has the incident photon-to-electron conversion efficiency 28.9% at 1000 nm (-5 V) and 6.2% at 1100 nm (-5 V). This photo-detector can be operated at a high-speed of 1 MHz. The experimental result suggests the potential applications of low band-gap conjugated polymers on near-infrared photo-detectors. (C) 2011 Elsevier B.V. All rights reserved.
Polymer photovoltaic devices with highly transparent cathodes
(2008-12-01)
Chen, Fang-Chung
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Wu, Jyh-Lih
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Hsieh, Kuo-Huang
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Chen, Wen-Chang
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Lee, Shih-Wei
In this paper, we demonstrate semi-transparent polymer solar cells employing a transparent cathode configuration, made of cesium carbonate (Cs2CO3)/silver (Ag)/indium tin oxide (ITO), which exhibited high transmittance in the visible regime. The device performance of the semi-transparent devices was significantly improved after thermal post-annealing and incorporating an Al counter-electrode (CE) grid. Further, the short-circuit current density increased almost linearly with the incident light intensity, suggesting efficient charge collection ability of the transparent cathode. Overall, the semi-transparent polymer solar cell exhibits a remarkable power conversion efficiency of 2.09%. (C) 2008 Elsevier B.V. All rights reserved.
Synthesis and characterization of well-dispersed multi-walled carbon nanotube/low-bandgap poly(3,4-alkoxythiophene) nanocomposites
(2010-08-01)
Liu, Cheng-Dar
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Shu, De-Yu
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Tsao, Ching-Ting
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Han, Jin-Lin
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Tsai, Feng-Yu
In this study, we prepared nanocomposites of multi-walled carbon nanotubes (MWCNTs) and low-energy-bandgap conjugated polymers incorporating 3,4-alkoxythiophene monomers. Poly(3,4-dihexyloxythiophene) (PDHOT) and poly(3,4-dimethoxythiophene-co-3,4-dihexyloxythiophene) [P(DMOT-co-DHOT)] have relatively low-energy-bandgaps (ca. 1.38 and 1.34 eV, respectively), determined from the onsets of absorbances in their UV-Vis spectra, because of the electron-donating effects of their alkoxy groups. MWCNTs have poor solubility in common organic solvents; after surface modification with alkyl side chains using the Tour reaction, however, the p-hexylaniline modified MWCNT derivative (MWCNT-HA) was readily dispersed in CHCl(3) and could be mixed with the low bandgap polymers. Scanning electron microscopy images revealed that MWCNT-HA was dispersed well in each polythiophene derivative; only a few MWCNT-HA bundles could be observed at a high MWCNT-HA content (>= 20 wt.%). The electrical conductivities of the MWCNTs/PDHOT composites were dependent on their MWCNT content, reaching 16 S/cm at 30 wt.% MWCNT-HA. We suspect that the two hexyloxy chains of PDHOT enhanced its solubility and allowed it to wrap around the surfaces of the MWCNTs more readily. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis and Properties of New Dialkoxyphenylene Quinoxaline-Based Donor-Acceptor Conjugated Polymers and Their Applications on Thin Film Transistors and Solar Cells
(2009-02-01)
Lai, Mei-Hsiu
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Chueh, Chu-Chen
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Chen, Wen-Chang
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Wu, Jyh-Lih
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Chen, Fang-Chung
Synthesis, properties, and optoelectronic device applications of four new bis-14-(2-ethyl-hexyloxy)-phenyllquinoxaline(Qx(EHP))-based donor-acceptor conjugated copolymers are reported, in which the donors are thiophene(T), ditbiophene(DT), dioetylfluorene(FO), and didecyloxyphenyleiie(OC10). The optical band gaps (E(g)) of PThQx(EHP), PDTQ(EHP), POCIODTQ(EHP), and PFODTQ(EHP) estimated from the onset absorption are 1.57, 1.65, 1.77, and 1.92 eV, respectively. The smallest E(g) of PThQx(EHP) among the four copolymers is attributed to the balanced donor/acceptor ratio and backbone coplanarity, leading to a strong intramolecular charge transfer. The hole mobilities obtained from the thin film transistor (TFT) devices of PThQx(EHP), PDTQ(EHP), POC10DTQ(EHP), and PFODTQ(EHP) are 2.52 x 10(4), 4.50 x 10(3), 4.72 x 10(5), and 9.31 x 10(4) cm(2) V(1) s(1), respectively, with the on-off ratios of 2.00 x 10(4), 1.89 x 10(3), 4.07 x 10(3), and 2.30 x 10(4). Polymer solar cell based on the polymer blends of PFODTQ(EHP), PThQx(EHP), POC10DTQ(EHP), and PDTQ(EHP) with [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) under illumination of AM1.5 (3.00 MW cm(-2)) solar simulator exhibit power conversion efficiencies of 1.75, 0.92, 0.79, and 0.43%, respectively. The donor/acceptor strength, molecular weight, miscibility, and energy level lead to the difference on the TFT or solar cell characteristics. The present study suggests that the prepared bisf4-(2-ethyl-hexyloxy)-phenyllquinoxaline donor-acceptor conjugated copolymers would have promising applications on electronic device applications. (C) 2008 Wiloy Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 973-985, 2009
Toward High-Performance Semi-Transparent Polymer Solar Cells: Optimization of Ultra-Thin Light Absorbing Layer and Transparent Cathode Architecture
(2013-04-01)
Chueh, Chu-Chen
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Chien, Shang-Chieh
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Yip, Hin-Lap
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Salinas, Jose Francisco
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Li, Chang-Zhi
Very small photoluminescent gold nanoparticles for multimodality biomedical imaging
(2013-05-01)
Lai, Sheng-Feng
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Chien, Chia-Chi
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Chen, Wen-Chang
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Chen, Hsiang-Hsin
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Chen, Yi-Yun
An original synthesis method based on X-ray irradiation produced gold nanoparticles (AuNPs) with two important properties for biomedical research: intense visible photoluminescence and very high accumulation in cancer cells. The nanoparticles, coated with MUA (11-mercaptoundecanoid acid), are very small (1.4 nm diameter); the above two properties are not present for even slightly larger sizes. The small MUA-AuNPs are non-cytotoxic (except for very high concentrations) and do not interfere with cancer cell proliferation. Multimodality imaging using visible light fluorescence and X-ray microscopy is demonstrated by tracing the nanoparticle-loaded tumor cells. (C) 2012 Elsevier Inc. All rights reserved.