Rational compatibility in ternary matrix enables all-small-molecule organic solar cells with over 16% efficiency
How to manipulate the phase separation and molecular arrangement to meet the need of efficient charge generation and extraction remains as the long-standing challenge in all-small-molecule organic solar cells (ASM-OSCs). Herein, small molecule acceptor Y7 as morphology modulator was incorporated into B1:BO-4Cl matrix to fabricate ternary ASM-OSCs. Y7 possesses excellent compatibility with acceptor BO-4Cl but poor compatibility with donor B1. Two acceptors prefer to form alloy-like formation in ternary blends due to their good compatibility, which is conducive to fine-tune the molecular arrangement for facilitating charge extraction. The inferior compatibility rooted from strong intermolecular interaction between Y7 and B1 can provide driving force to manipulate the phase separation between donor and acceptor for gaining well-formed nanofibrous and bi-continuous interpenetrating networks, leading to efficient charge separation, transport and collection in ternary blends. The ternary ASM-OSCs with 10 wt% Y7 in acceptors achieve a top-ranked power conversion efficiency of 16.28% with holistic improvement of short-circuit current density, open-circuit voltage and fill factor. This work opens a new avenue to optimize the morphology for further boosting the performance of OSCs.