Grain Boundary Elimination via Recrystallization‐Assisted Vapor Deposition for Efficient and Stable Perovskite Solar Cells and Modules

Abstract Vapor deposition is a promising technology for the mass production of perovskite solar cells. However, the efficiencies of solar cells and modules based on vapor‐deposited perovskites are significantly lower than those fabricated using the solution method. Emerging evidence suggests that large defects are generated during vapor deposition owing to a specific top‐down crystallization mechanism. Herein, a hybrid vapor deposition method combined with solvent‐assisted recrystallization for fabricating high‐quality large‐area perovskite films with low defect densities is presented. It is demonstrated that an intermediate phase can be formed at the grain boundaries, which induces the secondary growth of small grains into large ones. Consequently, perovskite films with substantially reduced grain boundaries and defect densities are fabricated. Results of temperature‐dependent charge‐carrier dynamics show that the proposed method successfully suppresses all recombination reactions. Champion efficiencies of 21.9% for small‐area (0.16 cm 2 ) cells and 19.9% for large‐area (10.0 cm 2 ) solar modules under AM 1.5 G irradiation are achieved. Moreover, the modules exhibit high operational stability, i.e., they retain >92% of their initial efficiencies after 200 h of continuous operation.