Synergistic Strategy of Anion and Cation at the SnO2/Perovskite Interface Constructing Efficient and Stable Solar Cells

The chemical regulation of SnO2 to enhance the properties of the buried interface in perovskite films is extensively investigated, but the underpinning mechanisms remain insufficiently understood. In this study, a synergistic strategy for cation fixation and anion diffusion by incorporating (3-amino-3-carboxypropyl) dimethylsulfonium chloride (Vitamin U, V-U) into a SnO2 colloidal solution is proposed. The cationic end (-COOH, -NH2) of V-U effectively inhibits the aggregation of SnO2 particles and promotes electron extraction and transport via chemical interactions. Simultaneously, the anionic end (Cl-) acts to eliminate surface hydroxyl groups on SnO2 and occupy oxygen vacancies. Crucially, a novel direct current polarization test is employed to elucidate the migration mechanism of Cl-, revealing that the migration principle of chloride ions in SnO2, and chloride ions can penetrate to the bottom of the perovskite layer, forming a wide bandgap thin layer that aids in energy level alignment and regulates charge transfer behavior. Ultimately, the device based on V-U-modified SnO2 achieves a champion efficiency of 25.27%. Moreover, it demonstrates impressive storage stability with a T90 of 5770 h and retains 86% of its initial efficiency after 1110 h of continuous light exposure.