Wet-Coating Temperature Control for Inorganic Perovskite Crystallization in Perovskite Solar Cells

All-inorganic cesium lead halide (CsPbX3, X = I–, Br–, Cl–) perovskite solar cells (PSCs) show great promise for photovoltaics due to their excellent thermal stability. However, their power conversion efficiency still lags behind that of hybrid perovskites, primarily due to the high defect densities caused by uncontrolled crystallization and the persistence of residual intermediate phases. To tackle this fundamental challenge, we developed a temperature-control strategy that regulates the wet-coating temperature during film deposition. This approach effectively modulates crystallization kinetics by balancing nucleation and growth rates, which significantly suppresses the formation of intermediate phases and promotes direct conversion to a phase-pure perovskite. As a result, the film morphology is greatly improved and trap states are reduced, leading to a remarkable enhancement in device performance. This study establishes the wet-coating temperature as a critical factor in controlling crystallization pathways and film quality, providing both deep mechanistic insights and a practical fabrication strategy for high-performance, operationally stable all-inorganic PSCs.