Browsing by Author "Chien, Shang-Chieh"

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1-(3-Methoxycarbonyl)propyl-2-selenyl-[6,6]-methanofullerene as a n-Type Material for Organic Solar Cells
(2011-07-01)
Chuang, Shih-Ching
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Chiu, Chih-Wei
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Chien, Shang-Chieh
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Chu, Chih-Wei
;
Chen, Fang-Chung
Demand for green and renewable energy is stimulating research into future materials for energy production. Thin films of materials possessing both electron accepting and donating functions play a unique role in solar energy technology because of their lightweight, flexibility, and economical, low-temperature, and large-area fabrication. A [60]fullerene derivative,[6,6]-2-selenyl-C(61)-butyric acid methyl ester (SeCBM), has been synthesized in three steps, namely through Friedel-Crafts acylation of selenophene, hydrazone formation and Bamford-Steven reaction. Organic photovoltaic device incorporating SeCBM and the conducting polymer P3HT exhibited an average power conversion efficiency of 3.26% and a champion efficiency as high as 3.81% under AM 1.5G irradiation. (C) 2011 Elsevier B.V. All rights reserved.
Chemically Doped and Cross-linked Hole-Transporting Materials as an Efficient Anode Buffer Layer for Polymer Solar Cells
(2011-11-22)
Sun, Ying
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Chien, Shang-Chieh
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Yip, Hin-Lap
;
Zhang, Yong
;
Chen, Kung-Shih
A series of cross-linkable hole-transporting materials (X-HTMs) consisting of indacenodithiophene, bithiophene, and thiophene units bookended by two triarylamine groups have been designed and synthesized to investigate their suitability as new anode buffer layer for bulk heterojunction polymer solar cells (PSCs). These X-HTMs can be thermally cross-linked at temperature between 150 and 180 C to form robust, solvent-resistant films for subsequent spin-coating of another upper layer. Energy levels of these cross-linked materials were measured by cyclic voltammetry, and the data suggest that these X-HTMs have desirable hole-collecting and electron-blocking abilities to function as an anode buffer layer for PSCs. In addition, by incorporating thiophene or fused ring units into the X-HTM backbone, it effectively improved the hole-carrier motilities. To further improve the conductivity and optical transparency for PSCs, the X-HTM films were p-doped with nitrosonium hexafluoroantimonate (NOSbF(6)). The doped X-HTM layers showed remarkably enhanced hole-current densities compared to neutral X-HTM under the same electric field bias. The properties of the doped X-HTM film as anode buffer layer has been investigated in PSCs. The resulting devices showed similar performance compared to those made using conducting polymer, poly(3,4-ethylene- dioxylenethiophene):poly(styrenesulfonate) (PEDOT:PSS), as the anode buffer layer. Moreover, a novel bilayer HTM structure consisting of a doped and a neutral layer was employed to exploit the feasibility of combining high conductivity from the doped X-HTM and good electron-blocking ability from the neutral X-HTM together. Interestingly, PSC devices based on this bilayer structure showed enhanced V(oc), J(sc), and FF compared to the devices with only a single-layer doped X-HTM. These results indicate that such X-HTMs are promising alternative materials to PEDOT:PSS as an anode buffer layer for polymer solar cells.
Enhanced power efficiency of single-layer white triplet polymer light-emitting diodes by blending with polymer oxides
(2008)
Chen, Yung-Shiuan
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Chien, Shang-Chieh
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Chen, Fang-Chung
;
Lian, Jan-Tian
;
Tsou, Chien-Lung
In this study, we have demonstrated enhanced performance of blue, red and white phosphorescent polymer light-emitting diodes (PLEDs) by blending poly(ethylene glycol) (PEG) into the active layer of the devices. By introducing PEG into the PLEDs, the turn-on voltages of these devices became lower than those of the conventional devices. In addition, the luminance efficiency and the external quantum efficiency of the blue and while phosphorescent PLEDs were both improved. Most important of all, because of the lower operating voltage, the higher power efficiency (7.3 lm/W, 1.5 lm/W, 4.61m1W) of the blue, red and white phosphorescent PLEDs than those of the control devices (2.9 lm/W, 1. 1 lm/W, 1. 9 lM/W) have been achieved, respectively. Finally, the improvement mechanism will be discussed.
Extended spectral response in organic photomultiple photodetectors using multiple near-infrared dopants
(2012-01-02)
Chuang, Shao-Tang
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Chien, Shang-Chieh
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Chen, Fang-Chung
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光電工程學系
;
顯示科技研究所
We demonstrate highly sensitive polymer photodetectors (OPDs) with spectral response extending from the ultraviolet to the near-infrared (NIR) region (similar to 1200 nm). After doping two NIR dopants, high external quantum efficiencies (similar to 5500%) and high responsivities (23.0 A/W) are achieved under a low reverse bias (-3.7 V). The high gains could be attributed to unbalanced carrier transport in the photoactive layer arising from the electron traps at the NIR dopants. This approach allows the ready preparation of OPDs exhibiting broad spectral responses and high quantum efficiencies simultaneously. (C) 2012 American Institute of Physics. [doi:10.1063/1.3675573]
Facile synthesis of a 56 pi-electron 1,2-dihydromethano-[60]PCBM and its application for thermally stable polymer solar cells
(2011)
Li, Chang-Zhi
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Chien, Shang-Chieh
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Yip, Hin-Lap
;
Chueh, Chu-Chen
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Chen, Fang-Chung
A facile synthesis was employed to make a 56 pi-electron methano-PC(61)BM with a very small 1,2-dihydromethano (CH(2)) group. This new fullerene derivative possesses high electron mobility (0.014 cm(2) V(-1) s(-1)) and higher LUMO energy level (0.15 eV) than PC(61)BM. Bulk hetero-junction devices based on using poly(3-hexylthiophene) and methano-PC(61)BM as active layer exhibited better performance and thermal stability than those using the PC(61)BM analogue.
Flexible polymer solar cells prepared using hard stamps for the direct transfer printing of polymer blends with self-organized interfaces
(2011)
Chen, Fang-Chung
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Chuang, Ming-Kai
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Chien, Shang-Chieh
;
Fang, Jheng-Hao
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Chu, Chih-Wei
A transfer printing technique allows the development of flexible photovoltaic devices. Blending poly (ethylene glycol) (PEG) in the photoactive layer causes the PEG molecules to migrate spontaneously to and weaken the bonding at the interface between the polymer film and the Si wafer, thereby facilitating the transfer process from a hard stamp to the receiving flexible substrate. The device fabricated using this transfer printing process had characteristics similar to those of the corresponding device prepared using a spin-coating process. Using hard stamps should help to realize the low-cost, high-throughput roll-to-roll fabrication of flexible solar cells.
Graphene-based chips fabricated by ultraviolet laser patterning for an electrochemical impedance spectroscopy
(2016-04-01)
Tseng, Shih-Feng
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Haiso, Wen-Tse
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Cheng, Pi-Ying
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Chung, Chien-Kai
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Lin, Yung-Sheng
This study aims to develop graphene-based impedance chips for an electrochemical impedance instrument fabricated by ultraviolet (UV) laser patterning. The finger-like electrode structure on multilayer graphene films coated on glass substrates was performed in a one-cycle laser patterning process. After a series of laser ablated line tests, the ablated line widths increased with increasing laser fluences. The optimal laser patterning parameters involved the laser fluence of 3.4 J/cm(2), scanning speed of 600 mm/s, and pulse repetition frequency of 100 kHz to remove completely a graphene electrode layer without damaging glass substrate. The patterned regions had no significant heat-affacted zones (HAZs) due to graphene materials with high thermal diffusivity. To clarify graphene removal completely, the patterned regions on graphene/glass substrates were detected by a Raman microscope. The developed impedance-sensing chips had been successfully applied to detect the phase separation for emulsions containing emulsifiers with 15%, 17.5%, and 20% Polysorbate 80 (Tween 80) concentrations. We found that the separation time increased with increasing the emulsifier concentration. (C) 2015 Elsevier B.V. All rights reserved.
High-mobility low-bandgap conjugated copolymers based on indacenodithiophene and thiadiazolo[3,4-c]pyridine units for thin film transistor and photovoltaic applications
(2011)
Sun, Ying
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Chien, Shang-Chieh
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Yip, Hin-Lap
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Zhang, Yong
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Chen, Kung-Shih
Two new semiconducting polymers based on indacenodithiophene and thiadiazolo[3,4-c]pyridine units were synthesized via Stille coupling polymerization. The polymers, PIDTPyT and PIDTDTPyT, exhibited main absorption bands in the range of 550-800 nm while their absorption maxima were located at around 700 nm in films. With two additional thiophene spacers, PIDTDTPyT showed a broader absorption band but a 20 nm blue-shifted maximum peak compared to that of PIDTPyT. Both of the polymers possess low bandgaps (similar to 1.6 eV) and deep energy levels for both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Organic field-effect transistors (OFETs) device measurements indicate that PIDTPyT and PIDTDTPyT have high hole carrier mobilities of 0.066 and 0.045 cm(2) V(-1) s(-1), respectively, with the on/off ratio on the order of 10(6). Bulk heterojunction photovoltaic devices consisting of the copolymers and PC(71)BM gave power conversion efficiencies (PCE) as high as 3.91% with broadband photo-response in the range of 300-800 nm. The relationships between the photovoltaic performance and film morphology, energy levels, hole mobilities are discussed.
High-performance single-layer polymer electrophosphorescent devices with polymer oxides
(2008)
Chen, Fang-Chung
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Chien, Shang-Chieh
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Lee, Shih-Wei
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光電工程學系
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顯示科技研究所
An enhanced power efficiency and a lower driving voltage of polymer electrophosphorescent devices have been demonstrated by blending poly(ethylene glycol) (PEG) into the active layer. The luminance efficiency of the device with Al cathode was up to 15.6 cd/A and the turn-on voltage was decreased to 5.6 V after the use of PEG. Further, the power efficiency was also improved to 5.0 lm/W. Moreover, similar improvement was also observed while Ca/Al or LiF/Ca/Al were used as the cathodes. The performance enhancement can be attributed to the interaction between Al and organic molecules with ethylene oxide groups, resulting in a better contact. (c) 2008 The Electrochemical Society.
Highly sensitive, low-voltage, organic photomultiple photodetectors exhibiting broadband response
(2010-09-06)
Chen, Fang-Chung
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Chien, Shang-Chieh
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Cious, Guan-Lin
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光電工程學系
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顯示科技研究所
Highly sensitive polymer photodetectors exhibiting broad spectral responses, ranging from the ultraviolet to the near-infrared (NIR) region, are obtained after incorporating an organic NIR dye into the device active layer. As a result, high external quantum efficiencies (>7000%) and high responsivities (32.4 A/W) are achieved at an extremely low operating voltage (-1.5 V). The high photomultiplation could be attribute to trapping of electrons, originating from the photogenerated electron/hole pairs, at the dye molecules, which effectively facilitates hole injection from the external circuit. The device preparation scheme presented herein opens up the possibility fabricating lost-cost, flexible organic photodetectors. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3488017]
HIGHLY-STABLE AND EFFICIENT POLYMER SOLAR CELLS INCORPORATING NANOSCALE BUFFER LAYERS INDUCED BY SPONTANEOUS VERTICAL PHASE SEPARATION
(2010)
Chien, Shang-Chieh
;
Yang, Hau-Chih
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Chen, Fang-Chung
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光電工程學系
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Department of Photonics
A nanoscale interlayer formed through spontaneous vertical phase separation enhances the efficiency and stability of polymer solar cells. Poly(ethylene glycol) molecules blended into the photoactive layer spontaneously migrate to the surface of the polymer blend to form the interfacial buffer, thereby reducing the contact resistance after undergoing chemical reactions with the AI atoms of the cathode. The vertical phase separation of PEG molecules in the device were investigated by using scanning electron microscopy and atomic force microscopy.
Improved thin film morphology and bulk-heterojunction solar cell performance through systematic tuning of the surface energy of conjugated polymers
(2012)
Sun, Ying
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Chien, Shang-Chieh
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Yip, Hin-Lap
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Chen, Kung-Shih
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Zhang, Yong
A detailed model study has shown that thin film morphology and bulk-heterojunction solar cell performance can be significantly improved by systematic tuning of the surface energy of the conjugated donor polymer through side-chain functionalization. Thiophene-flanked diketopyrrolopyrrole (DPP) moieties with different contents of cyanohexane side chains were incorporated into three low band-gap conjugated copolymers (PIDTDPP1, PIDTDPP2 and PIDTDPP3) consisting of indacenodithiophene (IDT) donors and DPP acceptors. The resulting polymers possessed good solubility in common organic solvents and showed similar energy levels, bandgaps, and hole mobilities. However, the introduction of cyano groups onto the terminal of side-chains significantly changed their surface energy. Topographical images obtained from atomic force microscopy (AFM) proved that a better matched surface energy between polymer and PC71BM had led to enhanced miscibility, which resulted in better BHJ film morphology. Consistent with the surface energy enhancement, the performance of BHJ photovoltaic devices increased from 0.97% for PIDTDPP1, to 2.16% for PIDTDPP2 then to 3.67% for PIDTDPP3. These results clearly reveal that tuning surface energy is an effective way to improve the morphology of the BHJ active layer and efficiency of the photovoltaic device.
Increased open circuit voltage in fluorinated benzothiadiazole-based alternating conjugated polymers
(2011)
Zhang, Yong
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Chien, Shang-Chieh
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Chen, Kung-Shih
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Yip, Hin-Lap
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Sun, Ying
Small band-gap conjugated polymers based on monofluoro- and difluoro-substituted benzothiadiazole were developed. Highly efficient polymer solar cells (PCE as high as 5.40%) could be achieved for devices made from these polymers.
Morphological study on pentacene thin-film transistors: the influence of grain boundary on the electrical properties
(2010-10-13)
Chen, Fang-Chung
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Chen, Ying-Pin
;
Huang, Yu-Jen
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Chien, Shang-Chieh
;
光電工程學系
We have prepared organic thin-film transistors (OTFTs) featuring pentacene molecules deposited at various substrate temperatures onto either hexamethyldisilazane (HMDS)- or poly(alpha-methylsyrene) (P alpha MS)-treated SiO(2) surfaces. As a result, we obtained different grain boundary densities in the conducting channel. Since the surface-modified devices featured similar grain boundary densities in their active layers, but displayed different electrical performances, we suspected that different trap states probably existed at the grain boundaries for the two different kinds of OTFTs. In addition, the surface morphologies of the initial layers featured grain boundaries that were rather blurred for the thin films prepared on the P alpha MS-treated substrates, whereas shallow boundaries appeared for the pentacene layers on the HMDS-treated surfaces. Therefore, we deduced that the different surface treatment processes resulted in different Schwoebel (step-edge) barriers, and hence, different morphologies. These results suggested that different trap states existed at the grain boundaries of the two types of surface-treated devices, leading to variations in the electrical performance, even though the grain boundary densities were similar.
Morphological study on pentacene thin-film transistors: the influence of grain boundary on the electrical properties
(2010-10-13)
Chen, Fang-Chung
;
Chen, Ying-Pin
;
Huang, Yu-Jen
;
Chien, Shang-Chieh
;
光電工程學系
We have prepared organic thin-film transistors (OTFTs) featuring pentacene molecules deposited at various substrate temperatures onto either hexamethyldisilazane (HMDS)- or poly(alpha-methylsyrene) (P alpha MS)-treated SiO(2) surfaces. As a result, we obtained different grain boundary densities in the conducting channel. Since the surface-modified devices featured similar grain boundary densities in their active layers, but displayed different electrical performances, we suspected that different trap states probably existed at the grain boundaries for the two different kinds of OTFTs. In addition, the surface morphologies of the initial layers featured grain boundaries that were rather blurred for the thin films prepared on the P alpha MS-treated substrates, whereas shallow boundaries appeared for the pentacene layers on the HMDS-treated surfaces. Therefore, we deduced that the different surface treatment processes resulted in different Schwoebel (step-edge) barriers, and hence, different morphologies. These results suggested that different trap states existed at the grain boundaries of the two types of surface-treated devices, leading to variations in the electrical performance, even though the grain boundary densities were similar.
Nanoscale functional interlayers formed through spontaneous vertical phase separation in polymer photovoltaic devices
(2009)
Chen, Fang-Chung
;
Chien, Shang-Chieh
;
光電工程學系
;
顯示科技研究所
;
Department of Photonics
A nanoscale interlayer formed through spontaneous vertical phase separation enhances the efficiency and stability of polymer solar cells. Poly(ethylene glycol) molecules blended into the photoactive layer spontaneously migrate to the surface of the polymer blend to form the interfacial buffer, thereby reducing the contact resistance after undergoing chemical reactions with the Al atoms of the cathode. The vertical phase separation of PEG molecules in the device were investigated by using depth profiling scanning electron microscopy and atomic force microscopy.
POLYMER SOLAR CELL AND MANUFACTURING METHOD THEREOF
(2011-04-07)
Chen, Fang-Chung
;
Chien, Shang-Chieh
A manufacturing method of a polymer solar cell is illustrated. A substrate and a first conductive layer formed thereon are provided. An organic active semiconductor material and a functional organic material, which features modifying an interface between an organic layer and electrodes, are dissolved in an organic solvent to form a blend. The blend is deposited on the first conductive layer by solution process. The organic solvent is removed, such that the functional organic material and the organic active semiconductor material exhibit phase separation so as to form an organic modified layer on the top of the organic active semiconductor layer. A second conductive layer is deposited by thermal coating on the organic modified layer. Importantly, the organic modified layer formed by spontaneous phase separation effectively modifies the interface between the organic active semiconductor layer and a second conductive layer, thereby enhancing efficiency of an organic solar cell.
Polymeric electrophosphorescent devices with low turn-on voltages and high power conversion efficiency by blending with poly(ethylene glycol)
(2007)
Chien, Shang-Chieh
;
Chen, Fang-Chung
;
光電工程學系
;
Department of Photonics
Phosphorescent polymer light-emitting diodes (PLEDs) with low turn-on and operating voltages and high power efficiency have been achieved by blending poly(ethylene glycol) (PEG) into the active layer. The luminance efficiency of the device with Al as the cathode achieves to 16cd/A. In addition, the device performance of this kind device with the Ca/Al and LiF/Ca/Al cathode architecture after blending of 10 wt.% PEG was also investigated. It is found that the driving voltages of the devicse were lower than those of the conventional devices, while the luminance efficiencies remind high. Consequently. a higher power conversion efficiency (14 lm/W) than that of the control device (9 lm/w) has been achieved.
Self-Assembled Poly(ethylene glycol) Buffer Layers in Polymer Solar Cells: Toward Superior Stability and Efficiency
(2012-01-12)
Chien, Shang-Chieh
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Chen, Fang-Chung
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Chung, Ming-Kai
;
Hsu, Chain-Shu
;
應用化學系
In this study, we have systematically investigated the mechanism behind the formation of nanoscale self-assembled polymer buffer layers at the cathode interfaces of polymer solar cells. Poly(ethylene glycol) (PEG) molecules in a polymer blend, comprising poly(3-hexylthiophene) and [6,6]-phenyl-C-61-butyric acid methyl ester, spontaneously migrated to the surface where they reacted with the Al cathode to form ohmic contacts. In terms of thermodynamics, the surface energy of the substrates played an important role in triggering the vertical-type morphology. From a kinetics point of view, PEG polymers having lower molecular weights readily underwent vertical phase separation prior to solidification of the polymer films, due to their higher mobilities, whereas PEG polymers of higher molecular weights tended to become trapped in the active layer. Employing this knowledge, we prepared organic photovoltaic cells exhibiting both high efficiency and appreciable improvement in stability.
Simple source/drain contact structure for solution-processed n-channel fullerene thin-film transistors
(2012-04-01)
Chen, Fang-Chung
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Tsai, Tzung-Han
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Chien, Shang-Chieh
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光電工程學系
;
顯示科技研究所
This paper describes a simple approach for reducing the contact resistances at the source/drain (S/D) contacts in solution-processed n-channel organic thin-film transistors (OTFTs). Blending poly(ethylene glycol) (PEG) into the fullerene semiconducting layer significantly improved the device performance. The PEG molecules in the blends underwent chemical reactions with the Al atoms of the electrodes, thereby forming a better organic-metal interface. Further, the rougher surface obtained after the addition of PEG could also increase the effective contact area, thereby reducing the resistance. As a result, the electrical properties of the devices were significantly improved. Unlike conventional bilayer structures, this approach allows the ready preparation of OTFTs with a low electron injection barrier at the S/D contacts. (c) 2012 Elsevier B.V. All rights reserved.