Browsing by Author "Yip, Hin-Lap"

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A Versatile Fluoro-Containing Low-Bandgap Polymer for Efficient Semitransparent and Tandem Polymer Solar Cells
(2013-10-01)
Chang, Chih-Yu
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Zuo, Lijian
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Yip, Hin-Lap
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Li, Yongxi
;
Li, Chang-Zhi
The versatility of a fluoro-containing low band-gap polymer, poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(5-fluoro-2,1,3-benzothia-diazole)] (PCPDTFBT) in organic photovoltaics (OPVs) applications is demonstrated. High boiling point 1,3,5-trichlorobenzene (TCB) is used as a solvent to manipulate PCPDTFBT:[6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) active layer morphology to obtain high-performance single-junction devices. It promotes the crystallization of PCPDTFBT polymer, thus improving the charge-transport properties of the active layer. By combining the morphological manipulation with interfacial optimization and device engineering, the single-junction device exhibits both good air stability and high power-conversion efficiency (PCE, of 6.6%). This represents one of the highest PCE valuesfor cyclopenta[2,1-b;3,4-b']dithiophene (CPDT)-based OPVs. This polymer is also utilized for constructing semitransparent solar cells and double-junction tandem solar cells to demonstrate high PCEs of 5.0% and 8.2%, respectively.
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
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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.
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
;
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.
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
;
Zhang, Yong
;
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.
Highly Efficient Polymer Tandem Cells and Semitransparent Cells for Solar Energy
(2014-05-01)
Chang, Chih-Yu
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Zuo, Lijian
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Yip, Hin-Lap
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Li, Chang-Zhi
;
Li, Yongxi
Highly efficient tandem and semitransparent (ST) polymer solar cells utilizing the same donor polymer blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) as active layers are demonstrated. A high power conversion efficiency (PCE) of 8.5% and a record high open-circuit voltage of 1.71 V are achieved for a tandem cell based on a medium bandgap polymer poly(indacenodithiophene-co-phananthrene-quinoxaline) (PIDT-phanQ). In addition, this approach can also be applied to a low bandgap polymer poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b\']dithiophene)-alt-4,7-(5-fluoro-2,1,3-benzothia-diazole)] (PCPDTFBT), and PCEs up to 7.9% are achieved. Due to the very thin total active layer thickness, a highly efficient ST tandem cell based on PIDT-phanQ exhibits a high PCE of 7.4%, which is the highest value reported to date for a ST solar cell. The ST device also possesses a desirable average visible transmittance (approximate to 40%) and an excellent color rendering index (approximate to 100), permitting its use in power-generating window applications.
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
;
Chen, Kung-Shih
;
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
;
Yip, Hin-Lap
;
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.
Toward High-Performance Semi-Transparent Polymer Solar Cells: Optimization of Ultra-Thin Light Absorbing Layer and Transparent Cathode Architecture
(2013-04-01)
Chueh, Chu-Chen
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Chien, Shang-Chieh
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Yip, Hin-Lap
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Salinas, Jose Francisco
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Li, Chang-Zhi