Asymmetric <i>π</i>‐Bridge Strategy Regulating Film‐Forming Kinetics for Over 19% Efficiency Organic Solar Cells

Abstract Blending morphologies are critical to bulk‐heterojunction (BHJ) organic solar cells (OSCs) to realize satisfactory photovoltaic performance. Therefore, rationally manipulating film‐forming kinetics is of great importance to building suitable phase‐separations to balance exciton dissociation and charge transport. Herein, by employing a unilateral π ‐bridge approach, a new acceptor, WA6 is reported to optimize the film‐forming process of active layers and their microstructures. Meanwhile, the possible influencing factors are proposed, including intermolecular electrostatic interactions and donor/acceptor compatibility in the vital solution‐to‐film transformation stage. Beneficial from the appropriate fibrous phase‐separation, the PM6:WA6 based solar cells refined exciton/charge properties, leading to 15.39% high efficiency and much greater than the control device based on the counterpart acceptor without π ‐bridge. Furthermore, the WA6 can serve as efficient guest component as well, and achieved 19.21% efficiency in the resultant ternary solar cells. This study provides a feasible approach to modulate the molecular aggregation and film‐forming procedure, for the construction of high‐performance OSCs with eligible blending morphologies.