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

ABSTRACT FAPbI 3 ‐based perovskite solar cells (PSCs) are more efficient than their MAPbI 3 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 PbI 2 causing incomplete conversion and PbI 2 residue. Here, we introduce thiacetazone additive into the PbI 2 precursor solution. This additive interacts with PbI 2 to significantly reduce PbI 2 ·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 PbI 2 . This multifunctional additive improves crystallization, substantially reduces residual PbI 2 , and effectively passivates defects in the perovskite film. Consequently, the optimized FAPbI 3 ‐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.