Enhancing the Performance of the MAPbI₃ Perovskite Solar Cells Synthesized in an Ambient Environment via Modification of the SnO₂ Electron Transport Layer

The tin oxide (SnO₂) electron transport layer (ETL) plays a vital role in the photo-conversion efficiency (PCE) and stability of organic-inorganic perovskite solar cells (PSCs). However, SnO₂ ETL-induced defects such as hydroxyl groups, oxygen vacancies, exposed Sn atoms, and dangling bonds hinder device performance. In this study, rubidium chloride (RbCl) has been used to modify the SnO₂ ETL. MAPbI₃ perovskite film formed on the RbCl-modified SnO₂ ETL exhibits improved crystallinity with enlarged grain size and reduced grain boundaries, and enhanced optical absorption. The Hall-effect measurements indicate the improved carrier mobility and the dark J-V curve shows the increment of electrical conductivity for the RbCl-modified SnO₂ ETL. X-ray photoelectron spectroscopy (XPS) results demonstrate the surface defects passivation of the perovskite layer by modifying the SnO₂ ETL. A champion PCE of 19.35% has been achieved for the RbCl-modified SnO₂ ETL-based devices with improved stability, while the control devices with unmodified SnO₂ ETL show a PCE of 17.18%.