Inhibiting Iodide Oxidation and Regulating Crystallization Synergistically Enable Efficient and Stable Air-Processed CsPbI ₂ Br Perovskite Solar Cells

The fabrication of perovskite solar cells under ambient conditions is more compatible with industrial production and commercial applications. Nevertheless, the iodide oxidation triggered by oxygen and uncontrolled perovskite crystallization pose major challenges to achieving satisfactory performance for the air-processed perovskite solar cell. Herein, we introduce pentaerythrityl tetrakis(3-mercaptopropionate) (PETMP) into the CsPbI 2 Br precursor solution to simultaneously inhibit the iodide oxidation and regulate perovskite crystallization for assembling high-performance CsPbI 2 Br perovskite solar cells in ambient air. The coordination interaction between PETMP and CsPbI 2 Br precursor stabilizes the precursor and slows perovskite crystallization. Moreover, the reductive –SH groups of PETMP convert the formed molecular iodine into iodide, effectively suppressing the iodide oxidation in the precursor solution and during the perovskite crystallization process. Upon PETMP addition, we fabricate a high-quality CsPbI 2 Br perovskite film with enlarged grains and decreased defect density in ambient air. Consequently, the air-processed CsPbI 2 Br perovskite solar cell without a hole-transport layer delivers an attractive efficiency of 15.20%, on a par with those of state-of-the-art counterparts assembled under a nitrogen atmosphere. In addition, the unencapsulated air-processed cell preserves 88.7% of its original efficiency after 1200 h of storage under ambient conditions.