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

Abstract

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, <b>TPDI2-Se</b>, was designed and synthesized for organic solar cells (OSCs). The NFA with smaller π-conjugated blades, namely, <b>TPDI-Se</b>, 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 <b>TPDI-Se</b>-based OSCs. However, a much higher PCE of 8.59% was achieved for <b>TPDI2-Se</b>-based devices owing to the π-extension in the peripheral panels. Moreover, the photovoltaic performance of <b>TPDI2-Se</b>-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 (<i>J</i>_sc) value of 17.21 mA/cm² was obtained for <b>TPDI2-Se</b>-based OSCs, which is among the highest <i>J</i>_sc 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.