Asymmetric Acceptors with Benzotriazine Central Core Achieving 19.63% Efficiency in Organic Solar Cells

Abstract Decreasing the symmetry of acceptors can enhance the molecular dipole moment, influence intermolecular packing and has been proven to be an efficient strategy to improve device performance. This study presents a new asymmetric design strategy to develop acceptors beyond conventional end group or side chain engineering. Specifically, an asymmetric unit, 1,2,4‐benzotriazine, is introduced as the central core in Y‐series acceptors. Additionally, monophenyl with and without fluorine, are substituted on the asymmetric core. This combination yields two asymmetric acceptors, H‐1 and H‐2F, both of which exhibit large dipole moments and strong packing interactions. Consequently, organic solar cells (OSCs) based on D18:H‐1 and D18:H‐2F achieved a high power conversion efficiencies (PCEs) of 18.56% and 18.85%, respectively. By incorporating BO‐4Cl into the D18:H‐2F blend, the ternary device achieved a remarkable efficiency of 19.63% due to the extended absorption and improved morphology. This work establishes a new asymmetric and easily modifiable central unit, highlights the advantages of asymmetric acceptors, and demonstrates their potential in OSCs.