Bin Zhao, Lei Zhu, Shaobing Xiong, Jinyang Yu, Xuelin Wang, Jingjing Zhao, Lixing Tan, Jingrong Zhang, Jiancheng Zhong, Lixuan Kan, Xiaoyun Wan, Kai Jiang, Hongxiang Li, Zaifei Ma, Yahui Liu, Haiming Zhu, Zhipeng Kan, Feng Liu, Zhenrong Sun, Junhao Chu, Qinye Bao
Abstract Reducing insufficient charge transport of bulk heterojunction (BHJ) photoactive layer is a key challenge for realizing efficient organic solar cells (OSCs). To address this issue, a synergistic modulation strategy is developed via introducing a highly crystalline p‐type organic semiconductor C8‐BTBT as a solid additive into a binary system consisting of a polymer donor PM6 and a nonfullerene acceptor L8‐BO, to simultaneously improve charge dynamics and phase morphologies. Resulting binary OSCs yield a remarkable efficiency of 20.1% with an impressive fill factor (FF) of 81.9%. The achieved FF is the highest reported so far for the PM6:L8‐BO community. The competitive advantages of the modified photoactive layer are attributed to matched electronic structures that facilitate exciton dissociation at donor: acceptor heterointerface, reduced charge trap densities, more balanced charge mobilities, and suppressed charge recombinations, evidently demonstrated by a series of transient characterization technologies and quantitative theoretical analyses. Moreover, the optimized micromorphology features uniform fibrillar structures with improved dispersity, significantly promoting electrical properties. This work sheds light on a promising strategy for addressing the BHJ charge transport challenge and further enhancing the performance of OSCs.