Journal
SCIENCE CHINA-CHEMISTRY
Volume 64, Issue 6, Pages 1031-1038Publisher
SCIENCE PRESS
DOI: 10.1007/s11426-021-9988-6
Keywords
polymer solar cells; conjugated polymer donor materials; donor-acceptor copolymers; non-equivalent D-A copolymerization
Categories
Funding
- National Key Research and Development Program of China [2019YFA0705900]
- MOST
- National Natural Science Foundation of China [51820105003, 21734008, 61904181]
- Guangdong Major Project of Basic and Applied Basic Research [2019B030302007]
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A novel non-equivalent D-A copolymerization strategy was proposed in this study to finely tune the physicochemical and photovoltaic properties of polymers by inserting more D units into the polymer backbone. The non-equivalent D-A copolymers showed improved performance in terms of energy levels, mobility, self-assembly, and crystallinity compared to the traditional alternate D-A copolymer. The non-equivalent D-A copolymer-based PSCs achieved higher power conversion efficiency with improved V-oc, J(sc) and FF simultaneously.
D-A copolymerization is a broadly utilized molecular design strategy to construct high efficiency photovoltaic materials for polymer solar cells (PSCs), and all the D-A copolymer donors reported till now are the alternate D-A copolymers with equal D-and A-units. Here, we first propose a non-equivalent D-A copolymerization strategy with unequal D- and A-units, and develop three novel non-equivalent D-A copolymer donors (PM6-D1, PM6-D2 and PM6-D3 with D/A unit ratio of 1.1:0.9, 1.2:0.8 and 1.3:0.7, respectively) by inserting more D units into the alternate D-A copolymer PM6 backbone to finely tune the physicochemical and photovoltaic properties of the polymers. The three non-equivalent D-A copolymers show the down-shifted highest occupied molecular orbital (HOMO) energy levels, higher hole mobility, higher degree of molecular self-assembly and higher molecular crystallinity with the increase of D-unit ratio in comparison with the alternate D-A copolymer PM6. As a result, all the three non-equivalent D-A copolymer-based PSCs with Y6 as acceptor achieve improved power conversion efficiency (PCE) with higher V-oc, larger J(sc) and higher FF simultaneously. Particularly, the PM6-D1:Y6 based PSC achieved a high PCE of 17.71%, which is significantly higher than that (15.82%) of the PM6:Y6 based PSC and is one of the highest performances in the binary PSCs.
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