Dimeric acceptors are expected to satisfy both excellent power conversion efficiency (PCE) and operational stability of organic solar cells (OSCs). However, comparing to highly planar and symmetrical monomer-like acceptors, the quite different steric/spatial configurations of dimeric acceptors affect device outcomes greatly. Herein, on basis of the same dimeric molecular platform that constructed by bridging central units of two monomer-like acceptor, diverse substituents (& horbar;OCH3 for D1, & horbar;CH3 for D2, and & horbar;CF3 for D3) are grafted on central units to regulate the three dimensions (3D) geometries of dimeric acceptors delicately. A systematic investigation reveals the substituent-dependent variation of energy level, absorption, and molecular packing behavior. Consequently, D2 acceptor, characteristic of more favorable configuration, affords a superior film morphology and charge transfer/transport dynamics in resulting OSCs, thus yielding an excellent PCE of 17.50% along with a good long-term stability. This work manifests the crucially important role of central substituents in constructing high-performance dimeric acceptors.

Diverse substituents (& horbar;OCH3 for D1, & horbar;CH3 for D2, and & horbar;CF3 for D3) are grafted on central units to regulate the 3D geometries of dimeric acceptors delicately. An efficiency of 17.50% is achieved for the D2-based devices along with a good long-term stability. This work manifests an important role of central substituents in constructing high-performance dimeric acceptors.