Non-fullerene electron acceptors constructed by four strong electron-withdrawing end groups: Potential to improve the photoelectric performance of organic solar cells by theoretical investigations

Abstract

Recent advances in non-fullerene acceptors have enabled the power conversion efficiencies of organic solar cells (OSCs) to exceed 16%. Fused-ring electron acceptors (FREAs) are some of the most widely investigated non-fullerene acceptors. Classical FREAs, containing two strong electron-withdrawing end groups, are typically constructed using linear architecture. Meanwhile, the development of 2D FREAs is rarely studied. Therefore, we proposed a series of novel 2D FREAs, namely, 2D-IC, 2D-ICT, 2D-ICTS and 2D-ICTSS, which were composed of four strong electron-withdrawing end groups linked by a 2D fused-ring core to form a rotational C2h-symmetric structure. Through theoretical calculations we found that as the degree of conjugation increased, the spectrum red shifted, the integrated absorption intensity was enhanced, and the hole-electron Coulomb attraction decreased. Compared with linear molecule ITOIC-2F, which had the same end groups, 2D-ICTSS exhibited two significant absorption peaks at red and near-infrared regions. In addition, its integrated absorption intensity was 1.8 times that of ITOIC-2F. Simultaneously, the hole-electron Coulomb attraction of 2D-ICTSS was smaller than that of ITOIC-2F. When alkyl chains were introduced, the electron mobility of 2D-ICTSS was estimated to be 1.98 times that of ITOIC-2F. Given that numerous critical factors (including absorption intensity, exciton separation, and electron mobility) of 2D-ICTSS were superior to those of ITOIC-2F, we propose that this rotational C2h-symmetric molecule is highly suitable as a high-performance electron acceptor. This molecule is expected to be an important candidate for the development of next-generation FREAs for high-performance OSCs.