All Air‐Processed n‐i‐p Perovskite Solar Cells Exceed 26% Efficiency Enabled by Thiacetazone Additive

FAPbI₃-based perovskite solar cells (PSCs) are more efficient than their MAPbI₃ counterparts, but their fabrication in air still faces more severe stability and reproducibility challenges. The underlying problem lies in the residual hygroscopic DMSO disrupts the perovskite crystallization by absorbing moisture, and an excessively rapid reaction between FAI and PbI₂ causing incomplete conversion and PbI₂ residue. Here, we introduce thiacetazone additive into the PbI₂ precursor solution. This additive interacts with PbI₂ to significantly reduce PbI₂·xDMSO complexes and form a mesoporous film conducive to the subsequent permeation of organic ammonium salt, while simultaneously interacting with FAI to moderate the reaction rate with PbI₂. This multifunctional additive improves crystallization, substantially reduces residual PbI₂, and effectively passivates defects in the perovskite film. Consequently, the optimized FAPbI₃-based PSCs achieve a record power conversion efficiency (PCE) of 26.52%-the highest value for air-processed n-i-p PSCs reported so far. When the PSCs are fabricated in a high-humidity atmosphere (70% RH), the PSCs still achieve a high PCE of 23.24%. Unencapsulated devices retain 92% of their initial PCE after 180 days in air (30-40% RH). This strategy provides a promising route to achieve efficient and storage-stable PSCs under ambient humidity.