Preparation of Dual-Asymmetric Acceptors via Selenium Substitution Combined with Terminal Group Optimization Strategy for High Efficiency Organic Solar Cells

Improving both the open-circuit voltage (VOC) and short-circuit current density (JSC) through the development of photovoltaic materials to achieve high power conversion efficiency (PCE) is critical and a significant challenge for organic solar cells (OSCs). Here, we designed novel dual-asymmetric acceptors A-SSe-TCF and A-SSe-LSF by simultaneously asymmetrically regulating the backbone and terminal groups and investigated their synergistic effects on photovoltaic performance in comparison with the monoasymmetric acceptor A-SSe-4F. The dual-asymmetric acceptors exhibit broader spectral absorption and larger half-molecule dipole moment differences, which favored the enhancement of JSC and the reduction of energy loss (Eloss). Among the binary blends, PM6:A-SSe-TCF exhibits superior phase separation, vertical phase distribution morphology, and more ordered π-π stacking compared to PM6:A-SSe-LSF and PM6:A-SSe-4F. As a result, OSCs based on PM6:A-SSe-TCF achieved a higher PCE of 18.53% with both higher VOC and JSC due to the suppressed nonradiative recombination and enhanced charge extraction capabilities. Furthermore, by incorporating A-SSe-TCF as the third component, the PM6:L8-BO:A-SSe-TCF-based device achieves a champion PCE of 19.73% without VOC loss on account of the decrement of Eloss. The novel dual-asymmetric strategy provides new insights into the molecular design and the improvement of PCE for OSCs.