Surface Reconstruction Engineering with Synergistic Effect of Mixed?Salt Passivation Treatment toward Efficient and Stable Perovskite Solar Cells

Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, lack of with mixture has been investigated, as well an in-depth understanding its mechanism. Here, systematic study on mixed-salt formamidinium bromide (FABr) coupled different F-substituted alkyl lengths ammonium iodide demonstrated. It obtained better device performance decreasing chain length the in presence FABr. Moreover, they unraveled synergistic mechanism through surface reconstruction engineering, where FABr dominates reformation via reacting excess PbI2. Meanwhile, passivates grain boundaries both and top bulk penetration. This engineer results high-quality fewer defects suppressed ion migration, leading champion efficiency 23.5% treatment. In addition, introduction moisture resisted groups presents more hydrophobic surface, thus enabling decorated devices excellent long-term stability under high humid atmosphere operational conditions.