π-Extension, Selenium Incorporation, and Trimerization: "Three in One" for Efficient Perylene Diimide Oligomer-Based Organic Solar Cells.

Perylene diimide (PDI) and the vinylene-bridged helical PDI oligomers are versatile building blocks for constructing nonfullerene acceptors (NFAs). In this contribution, a benzene-cored star-shaped NFA, namely, TPDI2-Se, was designed and synthesized for organic solar cells (OSCs). The NFA with smaller π-conjugated blades, namely, TPDI-Se, was synthesized for comparison. Using the commercially available PTB7-Th as the electron donor, the best power conversion efficiency (PCE) of 3.62% was obtained for TPDI-Se-based OSCs. However, a much higher PCE of 8.59% was achieved for TPDI2-Se-based devices owing to the π-extension in the peripheral panels. Moreover, the photovoltaic performance of TPDI2-Se-based OSCs is also superior to those of the parent NFA TPDI2 (PCE of 7.84%)- and the blade moiety PDI2-Se (PCE of 6.61%)- based ones. Additionally, a remarkable short-circuit current (Jsc) value of 17.21 mA/cm2 was obtained for TPDI2-Se-based OSCs, which is among the highest Jsc values reported in PDI-based OSCs. These results argue that the so-called "three in one" molecule design strategy of π-extension, selenium incorporation, and trimerization offers a robust approach to constructing high-performance PDI-based NFAs.