Browsing by Author "Huang, Jen-Hsien"

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A Strategic Buffer Layer of Polythiophene Enhances the Efficiency of Bulk Heterojunction Solar Cells
(2010-05-01)
Wei, Hung-Yu
;
Huang, Jen-Hsien
;
Ho, Kuo-Chuan
;
Chu, Chih-Wei
;
光電工程學系
We have developed polymer solar cells featuring a buffer layer of polythiophene (PT) sandwiched between the active layer and the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer. We attribute the improvement in power conversion efficiency of these polymer solar cells, relative to that of those based on poly(3-hexylthiophene):[6,6]-phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM), to a reduction in the degree of carrier recombination at the junction interface. Because the conductivity and the energy level of PT can be tuned simply by applying a bias to it in an electrolytic solution, we also investigated the effect of the energy level on the devices' performances. The power conversion efficiency of a solar cell containing a PT buffer layer reached 4.18% under AM 1.5 G irradiation (100 mW/cm(2)).
A ternary cascade structure enhances the efficiency of polymer solar cells
(2010)
Huang, Jen-Hsien
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Velusamy, Marappan
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Ho, Kuo-Chuan
;
Lin, Jiann-Tsuen
;
Chu, Chih-Wei
In this study, a novel solution-processed small molecule (TQTFA) for use as an electron donor has been incorporated into organic solar cells based on poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C71-butyric acid methyl (PC[70]BM). The combination of TQTFA with P3HT and PC[70]BM allows not only a broad absorption but also tuning of the inter energy level leading to a higher short-circuit current (J(SC)) and open-circuit voltage (V(OC)). The best performing devices exhibited a power conversion efficiency of 4.50%. The efficiency is increased by almost 15% when compared to the one without TQTFA.
Achieving efficient poly(3,4-ethylenedioxythiophene)-based supercapacitors by controlling the polymerization kinetics
(2011-08-01)
Huang, Jen-Hsien
;
Chu, Chih-Wei
;
光電工程學系
;
Department of Photonics
In this study, we have prepared a series of poly(3,4-ethylenedioxythiophene) (PEDOT) with various molecular weight by using an inhibitor, imidazole (Im). The X-ray diffraction (XRD) results show that the PEDOT with larger molecular weight enhances the polymer chain ordering and stacking which leads to higher conductivity. With increasing the amount of Im, the conductivity of PEDOT can be increased from 4.01 S cm(-1) (Im = 0.0 M) to 153.6S cm(-1) (Im = 1.8 M). Comparisons of the cyclic voltammetry (CV), it enables correlation between the conductivity and specific capacitance, which is important for understanding the electrochemical capacitive behavior of conjugated polymer for pseudo-capacitor application. The PEDOT prepared with 1.8M Im shows a specific capacitance of 124 F g(-1), which is 2.2 times larger than the one without Im (57 F g(-1)). (C) 2011 Elsevier Ltd. All rights reserved.
Annealing effect of polymer bulk heterojunction solar cells based on polyfluorene and fullerene blend
(2009-02-01)
Huang, Jen-Hsien
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Yang, Chuan-Yi
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Ho, Zhong-Yo
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Kekuda, Dhananjay
;
Wu, Meng-Chyi
Control of blend morphology at the nanoscale and high charge mobility is essential for polymer photovoltaic devices in terms of their power conversion efficiencies (PCE). In the case of bulk heterojunctions solar cells, both blend morphology and charge mobility are influenced by thermal treatment. In this manuscript, we study the effects of annealing temperature on polymer PV devices with blends of poly[9,9'-dioctyl-fluorene-co-bithiophene] (F8T2) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). The morphological changes of blended films were observed upon thermal annealing temperature near and above glass transition temperature (130 degrees C). Such microstructural transformations resulted in modified charge transport pathways and therefore greately influenced the device performance. The highest PCE of 2.14% with an open-circuit voltage (V(OC)) of 0.99 V and a short-circuit current (J(SC)) of 4.24 mA/cm(2) was achieved by device annealing at 70 degrees C for 20 min. (C) 2008 Elsevier B.V. All rights reserved.
Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes
(2011-02-14)
Hsu, Min-Hsiang
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Yu, Peichen
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Huang, Jen-Hsien
;
Chang, Chia-Hua
;
Wu, Chien-Wei
In this paper, we present evidence of balanced electron and hole transport in polymer-fullerene based solar cells by means of embedded indium-tin-oxide nanoelectrodes. Enabled by a controllable electrochemical deposition, the individual nanoelectrodes are uniformly enclosed by a poly (3,4-ethylenedioxythiophene) hole-conducting layer, allowing a relatively short route for holes to reach the anode and hence increasing the effective hole mobility. Consequently, the power conversion efficiency and photogenerated current are maximized with a deposition condition of 50 mu C, where the ratio of the electron to hole mobility is nearly unity. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556565]
Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes (vol 98, 073308, 2011)
(2011-03-14)
Hsu, Min-Hsiang
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Yu, Peichen
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Huang, Jen-Hsien
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Chang, Chia-Hua
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Wu, Chien-Wei
Controlled Growth of Nanofiber Network Hole Collection Layers with Pore Structure for Polymer-Fullerene Solar Cells
(2008-12-04)
Huang, Jen-Hsien
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Ho, Zhong-Yo
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Kekuda, Dhananjay
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Chu, Chih-Wei
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Ho, Kuo-Chuan
In this study, we compare a series of hole collector layers (HCLs) with pore structure fabricated via an electrochemical method to construct polymer-fullerene solar cells. The HCLs with a pore structure can offer a large interface to enhance hole collection; however, the series resistances are also increased by the relatively pore morphology. Photovoltaic device with the largest short circuit current (J(sc)) and efficiency is achieved using poly(3,4-propylenedioxythiophene) (PProDoT) as HCLs due to its highly porous structure and reasonable series resistance. By further optimizing the thickness of the HCLs in the solar cell, a power efficiency of 3.57% under simulated sun light is achieved.
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
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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
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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
;
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.
Effective Work Function Modulation of Graphene/Carbon Nanotube Composite Films As Transparent Cathodes for Organic Optoelectronics
(2011-08-01)
Huang, Jen-Hsien
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Fang, Jheng-Hao
;
Liu, Chung-Chun
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Chu, Chih-Wei
;
光電工程學系
In this study, we found that the work functions (Phi(w)) of solution-processable, functional graphene/carbon nanotube-based transparent conductors were readily manipulated, varying between 5.1 and 3.4 eV, depending on the nature of the doping alkali carbonate salt. We used the graphene-based electrodes possessing lower values of Phi(w) as cathodes in Inverted-architecture polymer photovoltaic devices to effectively collect electrons, giving rise to an optimal power conversion efficiency of 1.27%.
Effects of nanomorphological changes on the performance of solar cells with blends of poly[9,9 '-dioctyl-fluorene-co-bithiophene] and a soluble fullerene
(2009-01-14)
Huang, Jen-Hsien
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Ho, Zhong-Yo
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Kekuda, Dhananjay
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Chang, Yung
;
Chu, Chih-Wei
Controlled nanophase segregation within the blended films of a conjugated polymer and a soluble fullerene has enabled us to form a continuous transfer pathway for the carriers, thereby increasing the photocurrent generation for polymer photovoltaic devices. Here, we study the effects of nanomorphological changes on the performance of polymer solar cells using blended films of poly[9,9'-dioctyl-fluorene-co-bithiophene] (F8T2) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Different weight ratios of the F8T2 and PCBM blends in various solvents were studied at different annealing temperatures. The morphology of the films seems to be a strong function of the processing conditions. The power conversion efficiency (PCE) of the photovoltaic devices has improved significantly from 0.34% to 2.14% under air mass 1.5 simulated solar illumination (100 mW cm(-2)), which could be attributed to the nanomorphological changes in the films.
Efficient bilayer polymer solar cells possessing planar mixed-heterojunction structures
(2010)
Huang, Jen-Hsien
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Li, Kuang-Chieh
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Kekuda, Dhananjay
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Padhy, Hari Hara
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Lin, Hong-Cheu
We have investigated the influence of thermal annealing on the performance of polymer bilayer solar cell devices incorporating poly{2,6-(4,4-bis[2-ethylhexyl]-4H-cyclopenta[2,1-b;3,4-b'] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)} (PCPDTTBT) as the donor and two kinds of fullerenes (C(60), C(70)) as acceptors. The higher absorption of C(70) increased the external quantum efficiency in the spectral range 400-600 nm. We observed morphological changes of the polymer films when the pre-annealing temperature was near the crystalline temperature (T(c), 207 degrees C). These nanostructural transformations resulted in a modified interfacial morphology of the donor phases and, therefore, greatly influenced the device performance. Post-annealing treatment reorganized the interface between the donor and acceptor phases, leading to better contact. The highest power conversion efficiency (2.85%) was obtained when we performed device pre- and post-annealing both at 200 degrees C for 30 min; the open-circuit voltage was 0.69 V and the short-circuit current was 8.42 mA cm(-2).
Efficient bulk heterojunction solar cells based on a low-bandgap polyfluorene copolymers and fullerene derivatives
(2009-09-01)
Huang, Jen-Hsien
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Li, Kuang-Chieh
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Wei, Hung-Yu
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Chen, Po-Yen
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Lin, Lu-Yin
A low-bandgap polymer (PF-PThCVPTZ) consisted of fluorene and phenothiazine was designed and synthesized. With the donor-acceptor segment, the partial charge transfer can be built in the polymer backbone leading to a wide absorbance. The absorption spectrum of PF-PThCVPTZ exhibits a peak at 510 nm and an absorption onset at 645 nm in the visible range. As blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor, narrow bandgap PF-PThCVPTZ as electron donor shows significant solar cell performance. Under AM 1.5 G, 100 mA/cm(2) illumination, a power conversion efficiency (PCE) of 1.85% was recorded, with a short circuit current (J(SC)) of 5.37 mA/cm(2), an open circuit voltage (V(OC)) of 0.80 V, and a fill factor (FF) of 43.0%. (C) 2009 Elsevier B.V. All rights reserved.
Efficient organic optoelectronics with multilayer structures
(2012)
Kuo, Tsung-Hsien
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Chen, Fang-Chung
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Li, Juo-Hao
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Huang, Annie Tzuyu
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Huang, Jen-Hsien
In this study we developed efficient polymer solar cells (PSCs) and polymer light emitting diodes (PLEDs) incorporating multilayer structures prepared through solution processing. To prevent dissolution of the bottom layer by the subsequent layer, we used a polydimethylsiloxane stamp to transfer the film onto the target surface. The active layer of the PSCs consisted of a poly(3-hexylthiophene) (P3HT)-rich layer and a [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM)-rich layer; the active layer of the PLEDs consisted of a blue-polyfluorene as the light emitting layer (LEL) and poly (9,9-di-n-octylfluorene-alt-(1,4-phenylene-((4-sec-butylphenyl)imino-1,4-phenylene))) (TFB) as the electron blocking layer (EBL). We found that the efficiency of devices was readily manipulated by changing the constitution of each stacking layer. After optimizing the fabrication conditions for each functional layer, we obtained PSCs reaching a power conversion efficiency of 3.52%. The efficiency of PLEDs incorporating an EBL was 27% greater (reaching 4.7 cdA(-1)) than that prepared without an EBL layer.
Electrochemical characterization of the solvent-enhanced conductivity of poly(3,4-ethylenedioxythiophene) and its application in polymer solar cells
(2009)
Huang, Jen-Hsien
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Kekuda, Dhananjay
;
Chu, Chih-Wei
;
Ho, Kuo-Chuan
;
光電工程學系
The influence of solvent on the electrochemical property and conductivity of PEDOT has been investigated by electrochemical and physical characterizations. The PEDOT treated with different solvents reveals a different reversibility of ionic transport and cycling stability, which is associated with the conformational rearrangement from aggregated to linear polymer chains, as evidenced from atomic force microscopy (AFM). The conductivity of the PEDOT thin film can also be enhanced while the degree of linear polymer chains is higher. The application of highly conductive PEDOT thin film as a buffer layer in the polymer photovoltaic devices was realized. A PCE of 4.27% for photovoltaic devices based on P3HT-PCBM under simulated sun light is achieved by using a PEDOT thin film treated with DMSO.
Enhanced Carrier Collection and Light Harvesting of Polymer Solar Cells Using Embedded Indium-Tin-Oxide Nano-Electrods
(2010)
Hsu, Min-Hsiang
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Chang, Chia-Hau
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Huang, Jen-Hsien
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Chu, Chi-Wei
;
Yu, Peichen
Distinctive indium-tin-oxide (ITO) nanorods are employed to serve as buried electrodes for polymer-based solar cells. The embedded nano-electrodes allow three-dimensional conducting pathways for low-mobility holes, offering a highly scaffolded cell architecture in addition to bulk heterojunctions. As a result, the power conversion efficiency and photocurrent of a polymer cell with ITO nano-electrodes demonstrates an enhancement factor of up to similar to 13.1% and 10% respectively, compared to a conventional cell. Furthermore, ITO nanostructures improved optical absorption not only for a wide range of wavelengths, but also at large angles of incidence (AOIs). Hence, devices with 3-D nanoelectrodes exhibited nearly ideal angular response of J(sc), implying great potentials for polymer or other thin-film solar cells.
Enhanced spectral response in polymer bulk heterojunction solar cells by using active materials with complementary spectra
(2010-01-01)
Huang, Jen-Hsien
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Lee, Chuan-Pei
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Ho, Zhong-Yo
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Kekuda, Dhananjay
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Chu, Chih-Wei
We have fabricated organic photovoltaic devices with blends of poly[9,9'-dioctyl-fluorene-co-bithiophene] (F8T2) and fullerene as an electron donor and electron acceptor, respectively. A significant improvement of the photovoltaic efficiency was found in device by using active materials with complementary spectra. The different weight ratios of composite film were also performed to correlate between morphology and the device performance. A power conversion efficiency (PCE) up to 2.0% with an open-circuit voltage of 0.85 V and a short-circuit current (J(SC)) of 5.3 mA/cm(2), was achieved by blending the F8T2 with [6,6]-phenyl-C71-butyric acid methyl ester (PC[70]BM). (C) 2009 Elsevier B.V. All rights reserved.
Fabrication of multilayer organic solar cells through a stamping technique
(2009)
Huang, Jen-Hsien
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Ho, Zhong-Yo
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Kuo, Tsung-Hsien
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Kekuda, Dhananjay
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Chu, Chih-Wei
In this article, we demonstrate a simple and reliable stamping technique for fabricating multi-layer solar cells. A poly(di-methylsilane) (PDMS) stamp is used for transferring the active layers onto the substrate. An intermediate solvent treatment is introduced to temporarily modify the PDMS surface; therefore, the polymer film can be uniformly formed on top of the PDMS surface. This method is involves non-contaminative and non-invasive processes, therefore it can avoid possible degradation or contamination of the polymer film and the PDMS stamp can be reused. Devices realized through this stamping technique both by direct and inverted structures exhibited power conversion efficiencies of 3.2 and 2.83% respectively.
High performance dye-sensitized solar cells based on platinum nanoparticle/multi-wall carbon nanotube counter electrodes: The role of annealing
(2012-04-01)
Huang, Kuan-Chieh
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Wang, Ying-Chiao
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Chen, Po-Yen
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Lai, Yi-Hsuan
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Huang, Jen-Hsien
A composite film is coated on the FTO using a solution, containing a synthesized dispersant, poly(oxyethylene)-segmented imide (POEM), dihydrogen hexachloroplatinate (H2PtCl6), and multi-wall carbon nanotube(MWCNT); the thus coated FTO is used as the counter electrode (CE) for a dye-sensitized solar cell (DSSC). The annealing temperature of the composite film, in the range of 110-580 degrees C, is found to be crucial for optimizing its catalytic ability to obtain the best possible performance for the DSSC. About 47% loss in mass for the POEM/H2PtCl6/MWCNT composite is observed from 110 to 390 degrees C, due to not only the progressive formation of PtNPs from H2PtCl6 but the decomposition of POEM. Therefore, the efficiencies (eta) of DSSCs applying these CEs are enhanced from 1.28 +/- 0.08% (110 degrees C) to 8.47 +/- 0.21% (390 degrees C). The mass of the composite loses dramatically under heating above 390 degrees C, due to the decomposition of MWCNTs. The eta decreases to 7.77 +/- 0.15% at 450 degrees C because the decrease in surface roughness of film. PtNPs grow in sizes from 450 to 580 degrees C, resulting in the further decrease in catalytic ability of film and the observed eta from 7.77 +/- 0.15% to 7.19 +/- 0.21%. (C) 2011 Elsevier B.V. All rights reserved.