Imperfections Immobilization and Regeneration in Perovskite with Redox‐Active Supramolecular Assembly for Stable Solar Cells

Abstract Imperfections in metal halide perovskites, such as those induced by light exposure or thermal stress, compromise device performance and stability. A key challenge is immobilizing volatile iodine produced by iodide oxidation and regenerating impurities like elemental lead and iodine. Here, we address this by integrating a redox‐active supramolecular assembly of nickel octaethylporphyrin into perovskite film, functioning as both an immobilizer and redox shuttle. Decorated ethyl groups in porphyrin distorts the π ring, increasing the axial ligand adsorption capacity of central metal ion, while reducing intermolecular interactions and promoting iodine adsorption achieving a maximum uptake of 3.83 mg mg −1 to iodine. Adsorbed iodine transfers more electrons to Ni ions, leading to a weakened interaction within I−I bond and facilitating the production of iodide ions. Such a situation further enables selective oxidation of metallic lead defects to Pb 2+ . Porphyrin supramolecule facilitates hole transport across perovskite grain boundaries, leading to a champion device efficiency of 25.37 % for a 0.10 cm 2 active area, outperforms the value of control device being 23.96 %. Modified devices without encapsulation exhibit significantly enhanced stability, maintaining over 90 % of its initial performance after 1,000 hours of continuous 1‐sun illumination at maximum power point at 65 °C.