Regulation of Vapor‐Deposited Perovskite by Rubidium Chloride for Efficient and Stable Inverted Perovskite Solar Cells

ABSTRACT Vapor‐phase deposition techniques widely adopted in the coating and semiconductor industry are facilitating the consolidation and market penetration of perovskite solar cells (PSCs). However, the efficiency of inverted p‐i‐n PSCs prepared by vapor methods lags far behind that of solution methods. The multidimensional defects at the buried interface of the perovskite layer could be considered the largest obstacle to improving the photovoltaic performance of vapor‐processed devices, particularly in devices prepared by vapor‐solid‐reaction methods. In this study, a two‐step thermal evaporation method is adopted to fabricate the perovskite precursor film. An ultrathin layer of RbCl is preburied at the bottom of the precursor film, and then RbCl and PbI 2 are co‐evaporated. The introduced RbCl achieves a concurrent passivation effect towards multidimensional defects: (1) The predeposited RbCl layer reacts with PbI 2 , forming an ultrathin dielectric layer of RbPbI x Cl 3‐x , which acts as crystallization nuclei, thereby effectively reducing the void defect density at the buried interface; (2) the RbCl doped in the bulk phase reacts with excess PbI 2 to form (PbI 2 ) 2 RbCl, further improving the structural stability of perovskites. The optimized device exhibited an improved fill factor of up to 82.91% and a power conversion efficiency of 22.28%, making it a leading value among vapor‐processed inverted PSCs. Under ambient conditions, the packaged device retained 95% of the initial efficiency after 1200 h of output, proving that the synergistic passivation strategy results in a significant effect on improving device stability.