Browsing by Author "Hsiao, Yu-Sheng"

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All-solution-processed inverted polymer solar cells on granular surface-nickelized polyimide
(2009-07-01)
Hsiao, Yu-Sheng
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Chen, Chih-Ping
;
Chao, Ching-Hsun
;
Whang, Wha-Tzong
;
材料科學與工程學系
In this study, we prepared all-solution-processed inverted polymer solar cells (PSCs) incorporating two solution-processed electrodes-surface-nickelized polyimide films (NiPI films) as cathodes and high-conductivity poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) films as anodes-and an active layer with a bulk heterojunction morphology of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-buytyric acid methyl ester (PCBM). The granular Ni thin films, which exhibited good adhesion and high-conductivity (ca. 2778 S cm(-1)) on the polyimide (PI) substrates and possessed a work function different from that of pure Ni metal (WF, 5.4 eV). Using ultraviolet photoelectron spectroscopy, we determined that the WF of the NiPI films was ca. 3.9 eV. Prior to the coating of the photoactive layer, the surface of the NiPI films were treated with titanium(diisopropoxide)bis(2,4-pentanedionate) (TIPD) solution to facilitate the deposition of high-quality active layer and further as a hole blocking layer. The solution processed anodes (solvent-modified PEDOT:PSS films) were further coated and subjected to mild oxygen plasma treatment on the active layer. Short exposure (5 s) to the plasma improved the quality of the surface of the active layer for PEDOT:PSS deposition. These inverted PSCs on flexible granular NiPI films provided a power conversion efficiency of 2.4% when illuminated under AM 1.5 conditions (100 mW cm(-2)). The phenomenon of light absorption enhancement in those inverted PSCs was observed as indicated in reflective UV-vis, haze factor and external quantum efficiency (EQE) responses. The resulting fill factor (FF) of 0.43 is still significantly lower than the FF of 0.64 for standard devices. When compared to the planar structure, the improvement of absorbance of light and good haze factors was obtained for granular structure which suggests NiPI as a better back contact electrode through enhancing the light trapping and scattering in inverted PSCs. (C) 2009 Elsevier B.V. All rights reserved.
Chemical formation of palladium-free surface-nickelized polyimide film for flexible electronics
(2008-04-30)
Hsiao, Yu-Sheng
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Whang, Wha-Tzong
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Wu, Sheng-Chang
;
Chuang, Kuen-Ru
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材料科學與工程學系
Flexible polyimide (PI) films for flexible electronics were surface-nickelized using a fully solution-based process and excellent adhesion between the nickel and polyimide phases was observed. Polyimide substrates were modified by alkaline hydrolysis, ion exchange, reduction and nickel electroless deposition without palladium. Atomic force microscopy and field emission scanning electron microscopy were used to follow the growth of nickel nanoparticles (Ni-NPs) and nickel layers on the polyimide surface. The surface resistances of the Ni-NPs/PI films and Ni/PI films, measured using a four-point probe, were 1.6x10(7) and 0.83 Omega/cm(2), respectively. The thicknesses of Ni-NPs and the Ni layer on the polyimide surface were 82 nm and 382 nm, respectively, as determined by transmission electron microscopy, and the Ni layer adhered well to PI, as determined by the adhesive tape testing method. (c) 2008 Elsevier B.V. All rights reserved.
Controlling vertical alignment of phthalocyanine nanofibers on transparent graphene-coated ITO electrodes for organic field emitters
(2012)
Huang, Kuo-Jung
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Hsiao, Yu-Sheng
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Huang, Jen-Hsien
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Chu, Chih-Wei
;
Chen, Peilin
In this study, we developed a simple and efficient approach-using graphene coatings on ITO as transparent electrodes-for inducing the growth of 29H,31H-phthalocyanine (H2Pc) nanofiber arrays through a thermal evaporation process, with potential use in organic field emitters (FEs). By controlling the surface energy and temperature of the electrodes during evaporation, H2Pc molecules readily self-assemble, forming an out-of-plane morphology on reduced graphene oxide surfaces (rGO; surface energy: ca. 50 mJ m(-2)). The devices fabricated on rGO/indium tin oxide (FE-rGO) exhibited not only excellent FE performance but also outstanding anti-degradation capability during stability tests. This facile approach toward rGO coatings opens a new avenue for the transformation of small organic molecule films into vertically standing nanostructures on transparent electrodes, with various organic electronics applications.
Correlation between Exciton Lifetime Distribution and Morphology of Bulk Heterojunction Films after Solvent Annealing
(2010-05-20)
Huang, Jen-Hsien
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Li, Kuang-Chieh
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Chien, Fan-Ching
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Hsiao, Yu-Sheng
;
Kekuda, Dhananjay
We have synthesized a low-bandgap polymer, bithiazole-based polymer (PCPDTTBT) containing cyclopentadithiophene and thiophene units, and studied its opticophysical properties and morphologies in bulk heterojunction films after annealing. We used confocal optical microscopy in conjunction with a fluorescence module to record exciton lifetime images within photoactive layers of PCPDTTBT and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). These images, which were consistent with those recorded using atomic force microscopy and transmission electron microscopy, revealed that phase separation of PCPDTTBT and PCBM occurred during slow solvent evaporation. This phase separation not only provided bicontinuous pathways for carrier transport to the respective electrodes hut also enhanced the degree of polymer chain stacking, thereby improving the absorption and balancing the electron and hole mobilities. We tested the performance of solar cells incorporating PCPDTTBT and various fullerene derivatives. Under AM 1.5 G illumination (100 mW cm(-2)), a PCPDTTBT/bisPCBM-based solar cell exhibited a power conversion efficiency of 3.8%, with a short circuit current of 7.3 mA cm(-2), an open circuit voltage of 0.88 V, and a fill factor of 59.1%.
Dual-color electrochromic films incorporating a periodic polymer nanostructure
(2012)
Wei, Hung-Yu
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Hsiao, Yu-Sheng
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Huang, Jen-Hsien
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Hsu, Chih-Yu
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Chang, Feng-Chih
In this study, we used electrochemical deposition with a polystyrene (PS) bead template to prepare thin layers of poly(3,4-ethylenedioxythiophene) (PEDOT) that has a nanometer-scale honeycomb periodicity. To achieve dual-color electrochromic films, we then used pulsed electrochemical deposition to form polyaniline (PANI) layers on the rims of the PEDOT honeycomb film. Modifying the depositing charge density of PANI allowed tuning of the color of the composite films. We estimated the coloration efficiencies with respect to the values expected for corresponding amounts of pristine single layers of PEDOT and PANI. As a result of improved contact between the polymer film and the electrolyte, the coloration efficiencies of the structured composite films were much closer to their theoretical values than those of the corresponding bilayer composite films. Moreover, the switching times of the structured composite films were much faster than those of the bilayer composite films prepared without the nanostructures.
Facile Synthesis of Diamino-Modified Graphene/Polyaniline Semi-Interpenetrating Networks with Practical High Thermoelectric Performance
(2018-02-07)
Lin, Yen-Hao
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Lee, Tsung-Chi
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Hsiao, Yu-Sheng
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Ling, Wei-Keng
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Whang, Wha-Tzong
p-Phenediamino-modified graphene (PDG) has been newly synthesized via a facile green one-step chemical route as a functionalized graphene-based additive to copolymerize with aniline for fabricating innovative PDG/polyaniline conducting polymer composites containing very special semi-interpenetrating networks (S-IPNs). The S-IPNs not only provide additional pathways by creating chemically bonded PDG and PANI for smoothly transporting carriers but greatly reduce the amount of graphene required to less than a few percent could effectively improve the overall electrical conductivity, Seebeck coefficient, and thus the thermoelectric (TE) performance. The found optimized TE figure of merit (ZT) of 0.74 approaches a practical high level which is comparable or much higher than previously reported ones for TE polymers.
High-conductivity poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film for use in ITO-free polymer solar cells
(2008)
Hsiao, Yu-Sheng
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Whang, Wha-Tzong
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Chen, Chih-Ping
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Chen, Yi-Chun
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材料科學與工程學系
In this study, we devised a simple method to enhance the conductivity of poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate) (PEDOT:PSS) films through spin-coating with various surface-modified compounds, and then applied this technique to the preparation of ITO-free polymer solar cells (PSCs). The electrical conductivity of PEDOT: PSS films can be increased by more than two order of magnitudes merely by spin-coating a compound containing one or more polar groups - such as ethanol, methoxyethanol, 1,2-dimethoxyethane, and ethylene glycol - onto the films. In this paper, we discuss the phenomena occurring through conductivities, morphologies, and chemical properties of the modified PEDOT-PSS films as determined using Raman spectroscopy, a four-point probe, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The schematic 3D morphological model of directly solvent-modified PEDOT: PSS films is presumed for ITO-free devices. The desirable conductivity enhancements of these materials make them attractive candidates for use as anode materials in ITO-free PSCs.
Humidity-switch chromism of aniline-pentamer in Nafion
(2016-08-19)
Lin, Yen-Hao
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Hsiao, Yu-Sheng
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Lu, Hsiao-Chi
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Chen, Peilin
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Whang, Wha-Tzong
Aniline-pentamer (AP) in Nafion triggered with humidity content displays an interesting chromism from blue to pink, which is much wider of color shift than general polyaniline. Thermogravimetric analysis confirms the reversal color change related to the moisture content in the sample. IR absorption spectra make known AP having high degree of protonation at lower water content. UV-Vis absorption expose the chromism process having something more than just protonation. The change of electronic energy levels and PL spectra reveal that there must be a complex interaction in NaAP. Raman scattering mapping confirms that drying causes the - SO3- hydrophilic channels transforming to isolated domains dispersed in matrix, which induces heavy protonation and complexation of AP with - SO3- groups. We can infer that the interesting humidity-switch chromism is due to the reversible protonation/deprotonation as well as complexation of AP with - SO3- groups through the reversible change of Nafion\'s morphology.
Improving the Light Trapping Efficiency of Plasmonic Polymer Solar Cells through Photon Management
(2012-10-04)
Hsiao, Yu-Sheng
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Charan, Shobhit
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Wu, Feng-Yu
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Chien, Fan-Ching
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Chu, Chih-Wei
In this study, we have explored how light trapping efficiency can be enhanced by using gold nanoparticles (Au NPs) of various sizes and shapes on the front of polymer solar cells (PSCs) with the active layer-blends of poly(3-hexyl thiophene) and [6,6]-phenyl-C-61-butyric acid methyl ester. The light-concentrating behavior was enhanced after we had incorporated gold nanospheres or nanorods into the anodic buffer layer [based on poly(3,4-ethylenedioxythiophene):polystyrenesulfonate] to trigger various localized surface plasmon resonance (LSPR) bands. Comparison of the optical characteristics and the performance of the PSCs prepared with and without Au NPs, and we found that the UV-vis and wavelength-dependent photoluminescent spectral data corroborated with the device performance due to the photon management by considering the light scattering and LSPR effects at the active layer. The presence of Au NPs increased the power conversion efficiency to approximately 4.3% (an enhancement of 24%).
Improving the Light Trapping Efficiency of Plasmonic Polymer Solar Cells through Photon Management
(2012-10-04)
Hsiao, Yu-Sheng
;
Charan, Shobhit
;
Wu, Feng-Yu
;
Chien, Fan-Ching
;
Chu, Chih-Wei
In this study, we have explored how light trapping efficiency can be enhanced by using gold nanoparticles (Au NPs) of various sizes and shapes on the front of polymer solar cells (PSCs) with the active layer-blends of poly(3-hexyl thiophene) and [6,6]-phenyl-C-61-butyric acid methyl ester. The light-concentrating behavior was enhanced after we had incorporated gold nanospheres or nanorods into the anodic buffer layer [based on poly(3,4-ethylenedioxythiophene):polystyrenesulfonate] to trigger various localized surface plasmon resonance (LSPR) bands. Comparison of the optical characteristics and the performance of the PSCs prepared with and without Au NPs, and we found that the UV-vis and wavelength-dependent photoluminescent spectral data corroborated with the device performance due to the photon management by considering the light scattering and LSPR effects at the active layer. The presence of Au NPs increased the power conversion efficiency to approximately 4.3% (an enhancement of 24%).
Low-temperature formation of self-assembled 1,5-diaminoanthraquinone nanofibers: Substrate effects and field emission characteristics
(2011-04-01)
Huang, Kuo-Jung
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Hsiao, Yu-Sheng
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Whang, Wha-Tzong
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材料科學與工程學系
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Department of Materials Science and Engineering
In this study, we used thermal evaporation with a low sublimation temperature (42 degrees C) to deposit 1,5-diaminoanthraquinone (DAAQ) in various morphologies-including nanorods, nanocornerstones, and nanofibers-onto various substrates. Three major factors influenced the growth of vertically aligned DAAQ nanofibers on the electrodes: a low water contact angle (WCA) for the substrate and intermolecular hydrogen bonding and pi-pi interactions between the DAAQ molecules. On Au and Ti substrates (low-WCA), the DAAQ nanofibers DAAQ-Au and DAAQ-Ti, respectively, possessed great verticality and high aspect ratios; they also exhibited field emission characteristics, with maximum emission current densities of 0.31 and 0.65 mA/cm(2), respectively, at an applied electric field of 12 V/mu m. The turn-on electric fields for producing a current density of 10 mu A/cm(2) were 8.5 V/mu m for DAAQ-Au and 8.25 V/mu m for DAAQ-Ti. From the slopes of Fowler-Nordheim plots, we calculated the field enhancement factors (beta) of DAAQ-Au and DAAQ-Ti to be 447 and 831, respectively. Field emission stability studies revealed that the DAAQ nanofibers possessed outstanding anti-degrading capability. The emission current did not decrease, but rather increased slightly, after 3000 s. Given the advantages of this simple low-temperature process and the impressive anti-degrading field emission characteristics, such DAAQ nanofibers have great potential for use in various electronics applications (e.g., as organic field emitters). (C) 2011 Elsevier B.V. All rights reserved.
Molecular-weight-dependent nanoscale morphology in silole-containing cyclopentadithiophene polymer and fullerene derivative blends
(2011-11-01)
Huang, Jen-Hsien
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Chen, Fang-Chung
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Chen, Cheng-Lun
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Huang, Annie Tzuyu
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Hsiao, Yu-Sheng
We have investigated the effect of polymer molecular weight (MW) on the morphology and efficiency of bulk heterojunction (BHJ) solar cells comprised of poly[(4,4'-bis(2-ethyl-hexyl)dithieno[3,2-b: 2',3'-d] silole)-2,6-diyl-alt-(5,5'-thienyl-4,4'-dihexyl-2,2'-bithiazole)2,6- diyl] (Si-PCPDTTBT) and [6,6]-phenyl C(61) butyric acid methyl ester (PCBM). Striking morphological changes are observed in BHJ films upon the change of the polymer MW. Atomic force microscopy and transmission electron microscopy studies suggest that high MW polymer generated high degree of phase separation, leading to formation of an inter-penetrating network for carrier transport. The X-ray diffraction investigation indicated that increased pi-pi stacking in Si-PCPDTTBT with increasing polymer MWs results in an increase in hole mobility of Si-PCPDTTBT and electron mobility of PCBM as well as the red shift absorption spectrum in BHJ films. The solar cells based on PCBM with high-MW Si-PCPDTTBT deliver power conversion efficiencies of 3.33%. (C) 2011 Elsevier B.V. All rights reserved.
Morphological control of CuPc and its application in organic solar cells
(2008-10-15)
Hsiao, Yu-Sheng
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Whang, Wha-Tzong
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Suen, Shich-Chang
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Shiu, Jau-Ye
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Chen, Chih-Ping
We have prepared organic photovoltaic (OPV) cells possessing an ideal bulk heterojunction (BHJ) structure using the self-assembly of copper phthalocyanine (CuPc) as the donor material and fullerene (C(60)) as the acceptor. The variable self-assembly behavior of CuPc on a diverse range of substrates (surface energies) allowed us to control the morphology of the interface and the degree of carrier transportation within the active layer. We observed rod-like CuPc structures on indium-tin oxide (ITO), poly(3,4-ethylenedioxythiophene)poly(4-styrenesulfonate) (PEDOT: PSS) and Au substrates. Accordingly, the interfaces and continuing transport path between CuPc and fullerene domains could be greatly improved due to the ideal BHJ structure. In this paper, we discuss the mechanisms of producing CuPc rod-like films on ITO, PEDOT: PSS and Au. The OPV cell performance was greatly enhanced when a mixture of horizontal and vertical CuPc rods was present on the PEDOT: PSS surfaces, i.e. the power conversion efficiency was 50 times greater than that of the corresponding device featuring a planar CuPc structure.
Nanoscale Correlation between Exciton Dissociation and Carrier Transport in Silole-Containing Cyclopentadithiophene-Based Bulk Heterojunction Films
(2011-02-10)
Huang, Jen-Hsien
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Teng, Chin-Min
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Hsiao, Yu-Sheng
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Yen, Feng-Wen
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Chen, Peilin
Understanding the effects of conjugated polymer structures on exciton lifetimes and morphologies within bulk heterojunction (BHJ) films is a necessary step toward the development of better organic solar cells. Studying the impact of a polymer's structure on the optical, morphological, and performance characteristics of a device can lead to advances in the design of new polymers. In this study, we synthesized carbon- and silicon-bridged cyclopentadithiophene- (CPDT-) based polymers and determined their photophysical properties and morphologies by measuring the exciton lifetime distributions in their BHJ films The silicon-bridged CPDT-based polymer/[6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) BHJ exhibited a higher degree of luminescence quenching, suggesting that thermodynamically favorable mixing on the molecular scale and nanoscale phase separation occurred simultaneously in the blend film. We attribute this favorable morphology to the presence of strong pi-pi stacking in the silicon-bridged CPDT-based polymers. Under AM 1.5 G illumination (100 mA cm(-2)), a device incorporating the silicon-bridged CPDT-based polymer and PCBM (1:2, w/w) gave an overall power conversion efficiency of 3.5% with a short-circuit current of 9.0 mA cm(-2), an open-circuit voltage of 0.72 V, and a fill factor of 53.6%.
Nitroanilines enhancing the holographic data storage characteristics of the 9,10-phenanthrenequinone-doped poly(methyl methacrylate) photopolymer
(2013-01-05)
Ko, Cheng-Jung
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Hsiao, Yi-Nan
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Lin, Shiuan-Huei
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Chen, Po-Lin
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Whang, Wha-Tzong
This article describes an approach toward improving the characteristics of a photopolymer for holographic data storage application. The maximum diffraction efficiency (?max) and dynamic range (M#) of 9,10-phenanthrenequinone (PQ)-doped poly(methyl methacrylate; PMMA) both improved significantly after co-doping with one of three nitroanilinesN,N-dimethyl-4-nitroaniline (DMNA), N-methyl-4-nitroaniline (MNA), and 4-nitroaniline (pNA). In particular, the value of ?max increased from 38% for the PMMA/PQ system to 72% for the PMMA/PQ/DMNA system (a 1.89-fold improvement) and the value of M# increased accordingly from 2.7 to 7.3 (a 2.70-fold improvement). Thus, the holographic data storage characteristics of PMMA/PQ photopolymers can be improved through co-doping with nitroaniline compounds. We also investigated the mechanism of the nitroaniline-induced improvement in optical storage performance using proton nuclear magnetic resonance and X-ray photoelectron spectroscopy. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012
Organic Photovoltaics and Bioelectrodes Providing Electrical Stimulation for PC12 Cell Differentiation and Neurite Outgrowth
(2016-04-13)
Hsiao, Yu-Sheng
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Liao, Yan-Hao
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Chen, Huan-Lin
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Chen, Peilin
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Chen, Fang-Chung
Current bioelectronic medicines for neurological therapies generally involve treatment with a bioelectronic system comprising a power supply unit and a bioelectrode device. Further integration of wireless and self-powered units is of practical importance for implantable bioelectronics. In this study, we developed biocompatible organic photovoltaics (OPVs) for serving as wireless electrical power supply units that can be operated under illumination with near-infrared (NIR) light, and organic bioelectronic interface (OBEI) electrode devices as neural stimulation electrodes. The OPV/OBEI integrated system is capable to provide electrical stimulation (ES) as a means of enhancing neuron-like PC12 cell differentiation and neurite outgrowth. For the OPV design, we prepared devices incorporating two photoactive material systems-beta-carotene/N,N\'-dioctyl-3,4,9,10-perylenedicarboximide (beta-carotene/PTCDI-C8) and poly(3-hexylthiophene)/phenyl-C-61-butyric acid methyl ester (P3HT/PCBM)-that exhibited open circuit voltages of 0.11 and 0.49 V, respectively, under NIR light LED (NLED) illumination. Then, we connected OBEI devices with different electrode gaps, incorporating biocompatible poly(hydroxymethylated-3,4-ethyl-enedioxythiophene), to OPVs to precisely tailor the direct current electric field conditions during the culturing of PC12 cells. This NIR light-driven OPV/OBEI system could be engineered to provide tunable control over the electric field (from 220 to 980 mV mm(-1)) to promote 64% enhancement in the neurite length, direct the neurite orientation on chips, or both. The OPV/OBEI integrated systems under NIR illumination appear to function as effective power delivery platforms that should meet the requirements for wirelessly offering medical ES to a portion of the nervous system; they might also be a key technology for the development of next-generation implantable bioelectronics.
Performance of chromophore-type electrochromic devices employing indium tin oxide nanorod optical amplification
(2012-03-01)
Huang, Jen-Hsien
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Hsu, Min-Hsiang
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Hsiao, Yu-Sheng
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Chen, Peilin
;
Yu, Peichen
In this study, we used transparent and conductive indium tin oxide (ITO) nanorods, prepared through electron-beam evaporation onto ITO glass substrates, as electrodes for viologen-based electrochromic devices (ECDs). Although the shapes of these ITO nanorods could be controlled simply by manipulating the evaporation time, they always maintained their high optical transmittance. Scanning electron microscopy images revealed that the ITO rods were uniformly distributed on the ITO glass: they had large surface areas for the tethering of electrochromic molecules. As a result, the ITO nanorods functioned as optical amplifiers in the viologen-based ECDs, increasing the color contrast [Delta T (%)] from 38% to 61%. (C) 2011 Elsevier B.V. All rights reserved.
Selective growth and enhanced field emission properties of micropatterned iron phthalocyanine nanofiber arrays
(2011-11-01)
Huang, Kuo-Jung
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Hsiao, Yu-Sheng
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Whang, Wha-Tzong
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材料科學與工程學系
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Department of Materials Science and Engineering
In this study, we developed a simple method for the micropatterned growth of iron phthalocyanine (FePc) nanofiber arrays using a thermal evaporation process. By controlling the surface energy and the temperature of the substrate (T(sub)), we obtained FePc films featuring a grain-like (in-plane) morphology on Si surfaces (higher surface energy) and a fiber-like (out-of-plane) morphology on Ag surfaces (lower surface energy) within a certain range of values of T(sub). On the Ag surfaces, these temperature-induced FePc nanofibers featured a high aspect ratio (AR) of 30.3 +/- 3.6, with a mean length of 699 +/- 216 nm and a mean radius of 22.2 +/- 4.3 nm, as-prepared at a value of T(sub) of 240 degrees C. The FePc films obtained at values of T(sub) of 25, 120, 180, and 240 degrees C all possessed alpha-phase crystalline structures. Because the growth structures of the FePc molecules on the Si and Ag substrates were quite different, we could control the growth of micropatterned 1D FePc nanofiber arrays on previously patterned Ag/Si substrates. From the comparison of the field emission (FE) properties in different ARs of patterned devices, higher AR (30.3 +/- 3.6) of devices (FE-240-P; T(sub) of 240 degrees C) exhibited better FE performance than lower AR (6.0 +/- 2.6) of devices (FE-180-P; T(sub) of 180 degrees C). The FE current density of devices (T(sub) of 240 degrees C) increased from 0.13 mA/cm(2) for the unpatterned device (FE-240-N) to 6.77 mA/cm(2) for the patterned device (FE240- P) at an applied electric field of 12 V/mu m. The turn-on electric fields required to produce a current density of 10 mu A/cm(2) were 7.7 and 10.3 V/mu m for the patterned and unpatterned FePc emitters, respectively. From the slopes of Fowler-Nordheim plots, we estimated the field enhancement factors (beta) of FE-240-P and FE-240-N to be 314 and 329, respectively. Studies of the emission current stability revealed that the FePc nanofibers possessed outstanding anti-degrading capability. During stability tests, the micropatterned FePc emitter (FE-240-P) displayed an efficient emission current with fluctuations of less than 20%. Because this facile platform allows control over the morphologies of films of small organic molecules merely by tuning the surface energy of the substrates, such micropatterned- FePc nanofibers might have great applicability in practical field emitters. (C) 2011 Elsevier B.V. All rights reserved.
Surface Plasmonic Effects of Metallic Nanoparticles on the Performance of Polymer Bulk Heterojunction Solar Cells
(2011-02-01)
Wu, Jyh-Lih
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Chen, Fang-Chung
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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.
The investigation of donor-acceptor compatibility in bulk-heterojunction polymer systems
(2013-07-22)
Huang, Jen-Hsien
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Hsiao, Yu-Sheng
;
Richard, Eric
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Chen, Chun-Chao
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Chen, Peilin
The fullerene derivative, indene-C-60 bisadduct (ICBA), has been introduced into poly(3-hexylthiophene) (P3HT) to improve the efficiency of P3HT-based devices. However, we found that ICBA is not suitable for most low bandgap polymers. In this study, we have correlated the cell performance with surface energy between the donor and acceptor materials in a bulk-heterojunction cell. These results show that higher photocurrent can be attributed to the morphology improvement induced by larger surface energy difference (Delta gamma) between the low bandgap polymer and fullerene. These results also suggest that synthetic strategies which adjust the Delta gamma between donor and acceptor should be considered. (C) 2013 AIP Publishing LLC.