Alder‐Ene Reaction‐Mediated Suppression of Tin(II) Oxidation for Efficient Tin‐Lead Perovskite Solar Cells

Abstract Despite numerous studies have reported the inhibition of tin (II) oxidation in mixed tin‐lead halide perovskite, there remains a dearth of mechanistic information regarding how tin (II) undergoes oxidation in the precursor solution, particularly in terms of the involvement of DMSO. We here take advantage of density functional theory (DFT) to uncover that SnI 2 can coordinate with DMSO and react with singlet oxygen, resulting in the generation of Sn (IV). Moreover, our DFT simulations reveal that benzaldehyde oxime (BZHO) competes with SnI 2 in reacting with oxygen through the Alder‐ene reaction, hence effectively restraining the oxidation of tin (II), which is further verified by several experimental characterizations. Besides, the introduction of BZHO has also regulated the crystallization of the perovskite film and modified the electronic structure of the perovskite surface. As a result, the perovskite solar cells with the addition of BZHO demonstrate superior performance and operational stability, retaining 82 % of the initial PCE under continuous 1‐sun illumination for 800 hours. Furthermore, the efficiency of all‐perovskite tandem solar cells treated with BZHO reached 26.76 %. Therefore, this work presents a promising strategy for designing high‐performance and stable all‐perovskite tandem solar cells.