Morphology Optimization of the Photoactive Layer through Crystallinity and Miscibility Regulation for High-performance Polymer Solar Cells

On the premise of strongly crystalline materials involved, it is a challenge to control the phase separation of bulk-heterojunction donor/acceptor active layer to fabricate high-performance polymer solar cells (PSCs). Herein, we develop a molecular design strategy of the third component to synthesize three guest materials (namely BTPT, BTP-Th, and BTP-2Th) to address this issue. We investigate and reveal the effect of crystallinity and miscibility of the third component in controlling the phase separation of Y6-derivatives-based blend film. As a result, a remarkable power-conversion efficiency of 18.53% is obtained in the ternary PSC based on PTQ10:m-BTP-PhC6 with BTP-Th as the third component, which is a significant improvement with regard to the efficiency of 17.22% for the control binary device. Our study offers a molecular design strategy to develop a third component for building ternary PSCs in terms of crystallinity and miscibility regulation.