Abstract Defects in perovskite are key factors in limiting the photovoltaic performance and stability of perovskite solar cells (PSCs). Generally, choline halide (ChX) can effectively passivate defects by binding with charged point defects of perovskite. However, we verified that ChI can react with CsPbI3 to form a novel crystal phase of one‐dimensional (1D) ChPbI3, which constructs 1D/3D heterostructure with 3D CsPbI3, passivating the defects of CsPbI3 more effectively and then resulting in significantly improved photoluminescence lifetime from 20.2 ns to 49.4 ns. Moreover, the outstanding chemical inertness of 1D ChPbI3 and the repair of undesired δ‐CsPbI3 deficiency during its formation process can significantly enhance the stability of CsPbI3 film. Benefiting from 1D/3D heterostructure, CsPbI3 carbon‐based PSCs (C‐PSCs) delivered a champion efficiency of 18.05 % and a new certified record of 17.8 % in hole transport material (HTM)‐free inorganic C‐PSCs.
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