Dynamic Reversible Oxidation‐Reduction of Iodide Ions for Operationally Stable Perovskite Solar Cells under ISOS‐L‐3 Protocol

Abstract Despite rapid advancements in the photovoltaic efficiencies of perovskite solar cells (PSCs), their operational stability remains a significant challenge for commercialization. This instability mainly arises from light‐induced halide ion migration and subsequent oxidation into iodine (I₂). The situation is exacerbated when considering the heat effects at elevated temperatures, leading to the volatilization of I₂ and resulting in irreversible device degradation. Mercaptoethylammonium iodide (ESAI) is thus incorporated into perovskite as an additive to inhibit the oxidation of iodide anion (I⁻) and the light‐induced degradation pathway of FAPbI₃→FAI+PbI₂. Additionally, the formation of a thiol‐disulfide/I⁻‐I₂ redox pair within the perovskite film provides a dynamic mechanism for the continuous reduction of I₂ under light and thermal stresses, facilitating the healing of iodine‐induced degradations. This approach significantly enhances the operational stability of PSCs. Under the ISOS‐L‐3 testing protocol (maximum power point (MPP) tracking in an environment with relative humidity of ≈50% at ≈65 °C), the treated PSCs maintain 97% of their original power conversion efficieney (PCE) after 300 h of aging. In contrast, control devices exhibit almost complete degradation, primarily due to rapid thermal‐induced I₂ volatilization. These results demonstrate a promising strategy to overcome critical stability challenges in PSCs, particularly in scenarios involving thermal effects.