Metal Phosphorus Chalcogenide Nanosheet-Modified SnO₂ Electron Transport Layers for Efficient Perovskite Solar Cells

The electron transport layer (ETL) of tin dioxide (SnO₂) plays a pivotal role in n-i-p perovskite solar cells (PSCs) by facilitating the extraction of photogenerated electrons and blocking the transport of holes. However, the presence of oxygen vacancies in SnO₂ adversely affects the quality of the ETLs and impairs the electron transport properties, reducing the performance of PSCs. Here, we present a novel interfacial engineering route by incorporating an exfoliated two-dimensional (2D) metal-phosphorus-chalcogen complex of the SnPS₃ nanosheets into the SnO₂ ETL. The sulfur atoms in the SnPS₃ nanosheets fill the oxygen vacancies in SnO₂, reducing the trap state density. Meanwhile, the SnPS₃-modified SnO₂ layer exhibits an improved energy level alignment and enhanced electrical conductivity. As a result, a remarkable efficiency improvement from 21.51 to 23.01% was observed, accompanied by optimized stability. These results expand the application scenarios of 2D metal-phosphorus-chalcogen complexes and provide a novel approach to tune SnO₂-based interfaces for PSCs.