Trapping Tetravalent Tin and Protecting Stannous in Tin-Lead Mixed Perovskites for Efficient All-Perovskite Tandem Solar Cells

Tin-lead (Sn-Pb) mixed perovskite solar cells (PSCs), which serve as bottom subcells in all-perovskite tandem solar cells, are pivotal for developing highly efficient solar cells. However, the vulnerability of stannous (Sn2+) to spontaneous oxidation to harmful tetravalent tin (Sn4+) presents significant challenges. Here, a "mouse glue trap" strategy is proposed to mitigate this issue by introducing a multifunctional additive, oxamidic acid potassium salt (OAPS). This approach effectively traps undesired Sn4+ impurities through strong interactions between the oxaminic acid groups of OAPS and Sn4+ impurities. Additionally, OAPS, with its unique functional groups, can inhibit Sn2+ oxidation, passivate defects, alleviate stress, and improve crystalline quality in Sn-Pb mixed perovskite films. As a result, the enhanced Sn-Pb mixed narrow-bandgap PSCs incorporating OAPS achieve a power conversion efficiency of 22.04% and exhibit improved storage stability, with 91% retention after 3072 h of storage in an N2-filled glovebox. Moreover, all-perovskite tandem cells using OAPS-incorporated Sn-Pb narrow-bandgap PSCs as subcells demonstrate efficiencies of 27.17% and 28.31% for two-terminal and four-terminal tandems, respectively, presenting a straightforward approach to optimizing performance in Sn-Pb mixed PSCs and their tandems. A strategy of "rat glue trap" is proposed to solve the oxidation problem of tin (Sn). A multifunctional additive potassium oxyamine salt, which can effectively trap Sn4+ impurities and protect Sn2+ ions, is introduced to prepare highly efficient tin-lead mixed narrow-bandgap perovskite solar cells and all-perovskite tandem solar cells. image