Moisture-responsive crystallization strategy for efficient CsPbI3 solar cells fabricated under high-humidity conditions

The intrinsic phase instability of CsPbI₃ perovskites necessitates stringent fabrication conditions, significantly hindering the practical deployment. In the DMA-mediated CsPbI₃ nucleation system, the Cs⁺/DMA⁺ ion exchange critically governs the resulting film quality. Here, we employ a moisture-responsive crystallization strategy utilizing propyltriethoxysilane (PTES) to deposite CsPbI₃ under ambient air with high humidity (55%). We demonstrate that the siloxane groups can capture DMA⁺ in the intermediate DMAPbI₃, facilitating DMA⁺ extraction and Cs⁺ incorporation, thereby accelerating crystallization kinetics. This approach enables CsPbI₃ PSCs to achieve a power conversion efficiency (PCE) of 21.00% with an impressive fill factor (FF) of 86.1% while processing perovskite under relative humidity (RH) of 55%. Higher PCEs of 21.85% and 22.60% (certified 22.02%) were achieved for devices fabricated at a lower RH of 25% and for films spin-coated under an N₂ atmosphere followed by annealing in ambient air, respectively. Furthermore, PTES-treated devices exhibit excellent operational stability under ambient conditions.