Enabling Record‐Breaking 19.05% Efficiency Organic Solar Cells by Crystallization Engineering of Simple Nonfused Ring Electron Acceptors

We report a novel nonfused ring electron acceptor, 2BTh‐2Cl, featuring a chlorinated end group that significantly enhances intermolecular interactions of acceptors. 2BTh‐2Cl displays lower solubility but higher crystallinity than the analogue 2BTh‐2F. Owing to the similar molecular skeleton, 2BTh‐2Cl exhibits excellent miscibility with 2BTh‐2F while maintaining high crystallinity. By adopting a ternary blend strategy and introducing 2BTh‐2Cl into the D18:2BTh‐2F system, the intermolecular interactions between acceptors are significantly enhanced, promoting the formation of a high‐crystallinity acceptor alloy phase. Through this crystallization engineering strategy, the ternary blend film composed of D18:2BTh‐2F:2BTh‐2Cl demonstrates remarkable crystallinity and mobility, achieving a record‐breaking power conversion efficiency of 19.05%. This achievement sets a new benchmark in the field of organic solar cells based on nonfused ring electron acceptors. Overall, this work effectively improves the crystallinity and mobility of nonfused‐ring acceptors through rational molecular design and ternary‐blend strategy, culminating in highly efficient OSCs.