Synergistic Strategy of Anion and Cation at the SnO 2 /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.