Double-Halide Composition-Engineered SnO₂-Triple Cation Perovskite Solar Cells Demonstrating Outstanding Performance and Stability

State-of-the-art perovskite solar cells (PSCs) have exhibited a record-breaking power conversion efficiency (PCE) of 25.2% with remarkable operational stability, surpassing the PCE of silicon-based solar cells. In the pristine state, a bulk perovskite film often exhibits intrinsic interstitial/vacancies defects, and nonco-ordinated ions especially at the film surface and grain boundaries, leading to undesirable recombination losses and crippled PCE in the PSCs. To address this issue, we rationally designed an extrinsic double-halide passivation (DHP) treatment, composed of methylammonium bromide and chloride ions in different ratios, to tailor the morphology, intrinsic defects, and optical band gap of the bulk perovskite films. Owing to the better-aligned energy levels, suppressed grain boundary recombination losses, and cascade charge transfer, the champion DHP device delivered a PCE of ∼20.3%, which is a tremendous improvement compared to that of the reference device (PCE ∼18.0%). More importantly, the air, photo, and thermal stabilities of the PSC devices are all enhanced after passivation treatment. The DHP treatment proposed herein represents a facile, yet effective approach to elevate the efficiency and stability of the PSCs.