Bithiopheneimide鈥揇ithienosilole/Dithienogermole Copolymers for Efficient Solar Cells: Information from Structure鈥揚roperty鈥揇evice Performance Correlations and Comparison to Thieno[3,4-c]pyrrole-

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• 作者：Xugang Guo ; Nanjia Zhou ; Sylvia J. Lou ; Jonathan W. Hennek ; Roc铆o Ponce Ortiz ; Melanie R. Butler ; Pierre-Luc T. Boudreault ; Joseph Strzalka ; Pierre-Olivier Morin ; Mario Leclerc ; Juan T. L贸pez Navarrete ; Mark A. Ratner ; Lin X. Chen ; Robert P. H. Chang ; Antonio Facchetti ; Tobin J. Marks
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：November 7, 2012
• 年：2012
• 卷：134
• 期：44
• 页码：18427-18439
• 全文大小：848K
• 年卷期：v.134,no.44(November 7, 2012)
• ISSN：1520-5126

文摘

Rational creation of polymeric semiconductors from novel building blocks is critical to polymer solar cell (PSC) development. We report a new series of bithiopheneimide-based donor鈥揳cceptor copolymers for bulk-heterojunction (BHJ) PSCs. The bithiopheneimide electron-deficiency compresses polymer bandgaps and lowers the HOMOs鈥攅ssential to maximize power conversion efficiency (PCE). While the dithiophene bridge progression R₂Si鈫扲₂Ge minimally impacts bandgaps, it substantially alters the HOMO energies. Furthermore, imide N-substituent variation has negligible impact on polymer opto-electrical properties, but greatly affects solubility and microstructure. Grazing incidence wide-angle X-ray scattering (GIWAXS) indicates that branched N-alkyl substituents increased polymer 蟺鈥撓€ spacings vs linear N-alkyl substituents, and the dithienosilole-based PBTISi series exhibits more ordered packing than the dithienogermole-based PBTIGe analogues. Further insights into structure鈥損roperty鈥揹evice performance correlations are provided by a thieno[3,4-c]pyrrole-4,6-dione (TPD)鈥揹ithienosilole copolymer PTPDSi. DFT computation and optical spectroscopy show that the TPD-based polymers achieve greater subunit鈥搒ubunit coplanarity via intramolecular (thienyl)S路路路O(carbonyl) interactions, and GIWAXS indicates that PBTISi-C8 has lower lamellar ordering, but closer 蟺鈥撓€ spacing than does the TPD-based analogue. Inverted BHJ solar cells using bithiopheneimide-based polymer as donor and PC₇₁BM as acceptor exhibit promising device performance with PCEs up to 6.41% and V_oc > 0.80 V. In analogous cells, the TPD analogue exhibits 0.08 V higher V_oc with an enhanced PCE of 6.83%, mainly attributable to the lower-lying HOMO induced by the higher imide group density. These results demonstrate the potential of BTI-based polymers for high-performance solar cells, and provide generalizable insights into structure鈥損roperty relationships in TPD, BTI, and related polymer semiconductors.