1D Choline‐PbI 3 ‐Based Heterostructure Boosts Efficiency and Stability of CsPbI 3 Perovskite Solar Cells

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 CsPbI 3 to form a novel crystal phase of one‐dimensional (1D) ChPbI 3 , which constructs 1D/3D heterostructure with 3D CsPbI 3 , passivating the defects of CsPbI 3 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 ChPbI 3 and the repair of undesired δ ‐CsPbI 3 deficiency during its formation process can significantly enhance the stability of CsPbI 3 film. Benefiting from 1D/3D heterostructure, CsPbI 3 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.