Electrostatic Modulation of Central Units Enables High‐Performance Fused‐Ring Trimeric Acceptors

ABSTRACT Fused‐ring trimeric acceptor benefits from both the high symmetry/planarity of small‐molecule acceptors and the large glass transition temperature of polymeric acceptors, making it highly potential to achieve organic solar cells (OSCs) with excellent power conversion efficiencies (PCEs) and long‐term stabilities simultaneously. However, due to the structural complexity of ring‐fused trimeric acceptor, conveniently tuning its optoelectronic properties remains a significant challenge. Herein, the first family of optically and electrostatically tunable fused‐ring trimeric acceptors (CH34, CH35, and CH36) is constructed by incorporating electron‐donating triazatruxene, electron‐neutral triphenylene and electron‐withdrawing tricycloquinazoline as central planes, respectively. All the trimeric acceptors maintain the intrinsic rigidity and planarity of molecular skeleton, which endow them with very small reorganization energies and weak electron–phonon coupling. Moreover, the quite different electrostatic properties of central cores exert significant effects on the energy levels distribution and light harvesting capacity of acceptors. Consequently, CH36 achieves a good PCE of 16.73%, representing the best performance among ring‐fused trimeric acceptors. Remarkably, CH36‐based ternary OSCs further render an excellent PCE of 20.48% along with substantially improved operational stability. Our work demonstrates the great potential of fused‐ring trimeric acceptor for realizing both highly efficient and stable organic photovoltaics.