In this study, three nonfused-ring electron acceptors (2TT, 2TT-C6-F, and 2TT-C11-F) with the same steric hindrance groups (2,4,6-tripropylbenzene) are designed and synthesized and the impact of electron-withdrawing and lateral alkyl side chains on the performance of binary and ternary organic solar cells (OSCs) is explored. For the binary OSCs, 2TT-C11-F with IC-2F terminal groups and lateral undecyl side chains display a red shifted absorption spectrum and suitable energy levels, and the corresponding blend film exhibits appropriate phase separation and crystallinity. Thus, binary OSCs based on 2TT-C11-F achieve an impressive power conversion efficiency of 13.03%, much higher than the efficiencies of those based on 2TT (9.68%) and 2TT-C6-F (12.11%). In the ternary OSCs, 2TT with CC terminal groups and lateral hexyl side chains exhibit complementary absorption and cascade energy levels with a host binary system (D18:BTP-eC9-4F). Hence, the ternary OSCs based on 2TT achieve a remarkable efficiency of 19.39%, ranking among the highest reported values. The research yields comprehensive 2TT-series nonfused-ring electron acceptors, demonstrating their great potential for the fabrication of high-performance binary and ternary OSCs.
Keywords: end group engineering; nonfused ring electron acceptors; organic solar cells; side chain engineering; ternary blend strategy.
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