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Electron Acceptors with Varied Linkages between Perylene Diimide and Benzotrithiophene for Efficient Fullerene-free Solar Cells
B. Wang, W. Liu, H. Li, J. Mai, S. Liu, X. Lu, H. Li, M. Shi, C.-Z. Li*, and H. Chen*


In this work, we present two new electron acceptors, TriPDI and Fused-TriPDI, in which three perylene diimide (PDI) moieties are tethered to a benzotrithiophene (BTT) core via either single bonds (TriPDI) or ring-fusion (Fused-TriPDI). TriPDI connects three PDIs to BTT via carbon–carbon single bonds, resulting in a rotatable and highly twisted skeleton. Instead, Fused-TriPDI, made through oxidative ring-fusion of TriPDI, exhibits good structural rigidity and planarity, as well as effective conjugation between PDI and BTT. As a result, the fused molecule shows up-shifted energy levels, and enhanced absorption and charge mobility over the unfused one. The polymer solar cells (PSCs) with a PTB7-Th:Fused-TriPDI blend show the best power conversion efficiency of 6.19%, which is around three times higher than that with PTB7-Th:TriPDI.

J. Mater. Chem. A 5 , 9396 (2017)