Browsing by Author "Wu, Jyh-Lih"

Now showing 1 - 12 of 12

Cesium carbonate as a functional interlayer for polymer photovoltaic devices
(2008-05-15)
Chen, Fang-Chung
;
Wu, Jyh-Lih
;
Yang, Sidney S.
;
Hsieh, Kuo-Huang
;
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.
Flexible Polymer Photovoltaic Devices Prepared With Inverted Structures on Metal Foils
(2009-07-01)
Chen, Fang-Chung
;
Wu, Jyh-Lih
;
Lee, Chia-Ling
;
Huang, Wen-Che
;
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.
Morphological study of P3HT:PCBM blend films prepared through solvent annealing for solar cell applications
(2010-12-01)
Chen, Fang-Chung
;
Ko, Chu-Jung
;
Wu, Jyh-Lih
;
Chen, Wei-Chi
;
光電工程學系
We have systematically investigated the morphology of poly(3-hexylthiophene: P3HT) and [6,6]-phenyl C(61)-butyic acid methyl ester (PCBM) blend films prepared through a slow growth apparoch as a function of PCBM loading in the blends for bulk heterojunction solar cells. In addition to the electrical characterisitcs, the molecular ordering and crystallinity of the polymers was examined by using the UV-vis spectroscopy and grazing incidence X-ray diffraction. From the images of confocal laser scan microscopy, we were also able to in-situ monitor the phase separation of the P3HT:PCBM blends during the process of solvent evaporation. Finally, the conductive atomic force microscopy was utilized to probe the spatial distribution of the local current across the photoactive layer prepared with various P3HT:PCBM ratios. From the experimental results, we found that the distribution of PCBM molecules in the P3HT matrix became homogeneous after the solvent annealing process, even though the distribution of the PCBM molecules was not even in the beginning. Therefore, the higher device efficiency could be attributed to the better thin-film morphology of the polymer blends. (C) 2010 Elsevier B.V. All rights reserved.
Near-infrared laser-driven polymer photovoltaic devices and their biomedical applications
(2011-09-01)
Wu, Jyh-Lih
;
Chen, Fang-Chung
;
Chuang, Ming-Kai
;
Tan, Kim-Shih
;
光電工程學系
We demonstrate near-infrared laser-driven (NIRLD) organic photovoltaic devices (OPVs), which can directly convert 980 nm light into electrical power. We attribute the NIR photovoltaic response to the long-wavelength absorption of charge transfer (CT) states. Direct excitation through CT states might open up new avenues for harvesting the long-wavelength spectrum of solar irradiation. Further, because of the high transparency of biological tissue toward 980 nm light, these NIRLD OPVs might be a promising wireless electrical source for biological nanodevices.
PLASMONIC-ENHANCED POLYMER PHOTOVOLTAIC DEVICES INCORPORATING AU NANOPARTICLES
(2010)
Wu, Jyh-Lih
;
Lee, Chia-Lin
;
Chen, Fang-Chung
;
Kuo, Chun-Hong
;
Huang, Michael H.
We have improved the device performance of polymer photovoltaic devices (OPVs) by blending Au nanoparticles (NPs) into the anodic buffer layer. The unique optical properties of localized surface plasmon resonance (LSPR), triggered by Au NPs, was beneficial for improving the photocurrent of OPVs. The excitation of LSPR increased not only the exciton generation rate but also the exciton dissociation probability. As a result, the power conversion efficiency of OPVs has been significantly enhanced from 3.57 to 4.24%.
Plasmonic-enhanced polymer photovoltaic devices incorporating solution-processable metal nanoparticles
(2009-07-06)
Chen, Fang-Chung
;
Wu, Jyh-Lih
;
Lee, Chia-Ling
;
Hong, Yi
;
Kuo, Chun-Hong
We have explored the effect of gold nanoparticle (Au NP)-induced surface plasmons on the performance of organic photovoltaic devices (OPVs). The power conversion efficiency of these OPVs was improved after blending the Au NPs into the anodic buffer layer. The addition of Au NPs increased the rate of exciton generation and the probability of exciton dissociation, thereby enhancing the short-circuit current density and the fill factor. We attribute the improvement in device performance to the local enhancement in the electromagnetic field originating from the excitation of the localized surface plasmon resonance. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3174914]
Polymer photovoltaic devices with highly transparent cathodes
(2008-12-01)
Chen, Fang-Chung
;
Wu, Jyh-Lih
;
Hsieh, Kuo-Huang
;
Chen, Wen-Chang
;
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.
Spatial redistribution of the optical field intensity in inverted polymer solar cells
(2010-05-10)
Chen, Fang-Chung
;
Wu, Jyh-Lih
;
Hung, Yi
;
光電工程學系
;
顯示科技研究所
We have used indium tin oxide (ITO), a transparent conducting oxide, as an optical spacer to improve the performance of inverted polymer solar cells. The optical interference effect resulted in spatial redistribution of the optical field in the devices. Although the degree of light absorption in inverted cells was not increased, the resulting favorable distribution of photogenerated excitons probably decreased the level of exciton quenching near the electrodes. As a result, the introduction of the ITO optical spacer at an appropriate thickness increased the short-circuit current density and the overall power conversion efficiency. (C) 2010 American Institute of Physics. [doi:10.1063/1.3430060]
Surface Plasmonic Effects of Metallic Nanoparticles on the Performance of Polymer Bulk Heterojunction Solar Cells
(2011-02-01)
Wu, Jyh-Lih
;
Chen, Fang-Chung
;
Hsiao, Yu-Sheng
;
Chien, Fan-Ching
;
Chen, Peilin
We have systematically explored how plasmonic effects influence the characteristics of polymer photovoltaic devices (OPVs) incorporating a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). We blended gold nanoparticles (Au NPs) into the anodic buffer layer to trigger localized surface plasmon resonance (LSPR), which enhanced the performance of the OPVs without dramatically sacrificing their electrical properties. Steady state photoluminescence (PL) measurements revealed a significant increase in fluorescence intensity, which we attribute to the increased light absorption in P3HT Induced by the LSPR. As a result, the rate of generation of excitons was enhanced significantly. Furthermore, dynamic PL measurements revealed that the LSPR notably reduced the lifetime of photogenerated excitons In the active blend, suggesting that interplay between the surface plasmons and excitons facilitated the charge transfer process. This phenomenon reduced the recombination level of geminate excitons and, thereby, Increased the probability of exciton dissociation. Accordingly, both the photocurrents and fill factors of the OPV devices were enhanced significantly. The primary origin of this improved performance was local enhancement of the electromagnetic field surrounding the Au NPs. The power conversion efficiency of the OPV device incorporating the Au NPs improved to 4.24% from a value of 3.57% for the device fabricated without Au NPs.
Surface Plasmonic Effects of Nanostructures on the Performance of Polymer Solar Cells
(2015)
Chuang, Ming-Kai
;
Wu, Jyh-Lih
;
Chien, Shang-Chieh
;
Chen, Fang-Chung
;
光電工程學系
In this chapter, we review recent progress related to the incorporation of plasmonic nanostructures in organic photovoltaic devices (OPVs) as a means of enhancing power conversion efficiencies. We begin by describing the fundamental properties of surface plasmons (SPs). We then outline the two primary schemes that are commonly employed for excitation of the SPs: the use of noble metal particles to trigger the SPs and the creation of propagating surface plasmon polaritons (SPP) through approaches that can overcome the problem of momentum mismatch (e. g., periodic corrugation at the metal-dielectric interface). Next, we discuss some recent remarkable approaches toward increasing the light absorption efficiency of OPVs, highlighting three categories of plasmonic structures that enhance the performance of OPVs. Finally, we provide a brief outlook regarding the future use of SPs in high-efficiency OPVs.
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
;
Chueh, Chu-Chen
;
Chen, Wen-Chang
;
Wu, Jyh-Lih
;
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
Upconversion effects on the performance of near-infrared laser-driven polymer photovoltaic devices
(2012-10-01)
Wu, Jyh-Lih
;
Chen, Fang-Chung
;
Chang, Shu-Hao
;
Tan, Kim-Shih
;
Tuan, Hsing-Yu
We have explored the upconversion (UC) effects resulting from the presence of NaYF4:Yb/Er nanocrystals in near-infrared laser-driven organic photovoltaic devices (OPVs). Illumination of these UC nanomaterials with monochromatic light (980 nm) led to emission of visible light, which was subsequently absorbed by the polymer photoactive layer. We infer that both the long-wavelength charge-transfer absorption of the polymer blend and the UC effect contributed to the obvious near-infrared photovoltaic response. The resulting UC effects led to noticeable enhancements in the photocurrent and the efficiencies of the OPV devices under illumination at 980 nm. (c) 2012 Elsevier B.V. All rights reserved.