Scalable Impregnation Method for Preparing a Self-Assembled Monolayer in High-Performance Vapor-Deposited Lead-Halide Perovskite Solar Cells

The power conversion efficiency (PCE) of inverted lead-halide perovskite solar cells (PSCs) via vapor deposition has undergone significant enhancement through the incorporation of a self-assembled monolayer (SAM) serving as the hole transport layer. To achieve high-performance PSCs, the SAM layer needs to maintain a dense and high-coverage configuration during the fabrication process. Our investigation revealed that during solid-vapor reaction, conditions of high temperature and low pressure can potentially lead to the migration of SAM molecules, particularly those adsorbed on the surface but have not yet formed covalent bonds. In this study, to overcome this limitation, we have developed an impregnation process for mixed SAM molecules with (4-(7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid (4PADCB) and glycine hydrochloride (GH), which reduces the agglomeration of SAM molecules and enhances their strong anchoring ability with the substrate, thereby maintaining an extremely high coverage rate even in the high-temperature and low-pressure environment of solid-vapor reactions. Consequently, champion efficiencies of 22.15% (0.16 cm²) and 19.18% (5 cm × 5 cm module) are achieved, which is the highest record for inverted PSCs based on vapor deposition. Moreover, the impregnation process of the SAM layer has the advantages of reusability, good uniformity, and low cost, which has very broad commercial prospects.