Journal
CHEMISTRY OF MATERIALS
Volume 32, Issue 7, Pages 3254-3261Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.0c00459
Keywords
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Funding
- National Natural Science Foundation of China [91633301, 21734008, 51820105003]
- Basic and Applied Basic Research Major Program o f Guangdong Province [2019B030302007]
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Molecular frontier orbital energy level and aggregation behavior regulation of polymer donors are feasible ways to improve the photovoltaic performance of polymer solar cells (PSCs). Here, we design and synthesize a new D-A copolymer donor PBQ10 based on bithienyl benzodithiophene D-unit and monoalkoxy-substituted bifluoroquinoxaline A-unit, which shows an obviously downshifted highest occupied molecular orbital energy level in comparison with the control polymer PBQ7 with a dialkoxyphenyl substituent on the bifluoroquinoxa-line A-unit. Moreover, PBQ10 exhibits more preferential face-on molecular orientation and tighter pi-pi stacking in the vertical direction of the substrate than PBQ7, which significantly improves the hole mobility of PBQ10 to 5.22 X 10(-4) cm(2) V-1 s(-1) in comparison with that (1.71 x 10(-4) cm(2) s(-1)) of PBQ7. As a result, the PBQ10-based PSC with Y6 as the acceptor demonstrates an impressive power conversion efficiency (PCE) of 16.34% with simultaneously increased open-circuit voltage and fill factor, which is significantly increased compared with the PBQ7-based PSC with a PCE of 13.45% and is one of the highest PCEs in binary PSCs. The result suggests that rational side-chain optimization of the polymer donor is an efficient way to regulate the molecular energy level and self-assembly feature and thus to improve the PCE of PSCs.
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