Molecular design towards two-dimensional electron acceptors for efficient non-fullerene solar cells

Abstract Non-fullerene polymer solar cells (NF-PSCs) have gained wide attention recently. Molecular design of non-fullerene electron acceptors effectively promotes the photovoltaic performance of NF-PSCs. However, molecular electron acceptors with 2-dimensional (2D) configuration and conjugation are seldom reported. Herein, we designed and synthesized a series of novel 2D electron acceptors for efficient NF-PSCs. With rational optimization on the conjugated moieties in both vertical and horizontal direction, these 2D electron acceptors showed appealing properties, such as good planarity, full-spectrum absorption, high absorption extinction coefficient, and proper blend morphology with donor polymer. A high PCE of 9.76% was achieved for photovoltaic devices with PBDB-T as the donor and these 2D electron acceptors. It was also found the charge transfer between the conjugated moieties in two directions of these 2D molecules contributes to the utilization of absorbed photos, resulting in an exceptional EQE of 87% at 730 nm. This work presents rational design guidelines of 2D electron acceptors, which showed great promise to achieve high-performance non-fullerene polymer solar cells.