Interfacial Crosslinking for Efficient and Stable Planar TiO2 Perovskite Solar Cells

Abstract The buried interface between the electron transport layer (ETL) and the perovskite layer plays a crucial role in enhancing the power conversion efficiency (PCE) and stability of n–i–p type perovskite solar cells (PSCs). In this study, the interface between the chemical bath deposited (CBD) titanium oxide (TiO 2 ) ETL and the perovskite layer using multi‐functional potassium trifluoromethyl sulfonate (SK) is modified. Structural and elemental analyses reveal that the trifluoromethyl sulfonate serves as a crosslinker between the TiO 2 and the perovskite layer, thus improving the adhesion of the perovskite to the TiO 2 ETL through strong bonding of the ─CF 3 and ─SO 3 − terminal groups. Furthermore, the multi‐functional modifiers reduced interface defects and suppressed carrier recombination in the PSCs. Consequently, devices with a champion PCE of 25.22% and a fill factor (FF) close to 85% is achieved, marking the highest PCE and FF observed for PSCs based on CBD TiO 2 . The unencapsulated device maintained 81.3% of its initial PCE after operating for 1000 h.