Solid‐State Crystallization Regulation Enables High‐Performance Thermally Evaporated CsPbI ₂ Br Perovskite Solar Cells

ABSTRACT Thermal evaporation is an industry‐compatible deposition technique with strong potential for scalable inorganic perovskite solar cells (PSCs), yet the performance of fully thermally evaporated CsPbI ₂ Br devices remains constrained by poorly controlled solid‐state crystallization, defect formation, and the unrevealed solid‐state diffusion–crystallization mechanisms. Here, we report an effective solid‐state crystallization regulation strategy for thermally evaporated CsPbI ₂ Br, enabled by a thermally evaporated molecular regulator, dibenzo‐18‐crown‐6 (DC), as a transient crystallization modulator. In situ measurements demonstrated that DC coordinates with Pb ^{2 +} in the evaporated precursor stack, retarding solid‐state nucleation and enabling more complete precursor diffusion and ordered grain growth during annealing. As a result, the DC‐modified CsPbI ₂ Br films exhibit substantially enhanced crystallinity, enlarged grain size, reduced trap‐state density, and enhanced optoelectronic properties, while preserving the intrinsic bandgap of 1.92 eV. Solar cells fabricated with these films deliver a champion power conversion efficiency of 15.85%, representing the highest efficiency reported to date for thermally evaporated CsPbI ₂ Br PSCs. Moreover, large‐area (50 × 50 mm ² ), sharply patterned perovskite films are readily fabricated using shadow masks, highlighting the scalability and manufacturing compatibility of this approach.