Ion‐Mediated Self‐Healing Strategy Enabling Efficient and Stable ETL‐Free Perovskite Solar Cells

Abstract Perovskite solar cells without electron transport layers (ETL‐free PSCs) have garnered increasing attention in recent years due to their simplified fabrication process and low production costs. However, non‐radiative recombination of charge carriers and band energy mismatch at the interface significantly limit device performance. Here, we propose an ion‐mediated self‐healing strategy introducing an indium sulfate (ln 2 (SO 4 ) 3 ) functional layer at the buried interface of the perovskite. The ln 3+ exhibits gradient doping at the buried interface, acting as a redox buffer to oxidize Pb 0 to Pb 2+ , while the generated ln + reduces I 0 to I − , forming a self‐healing redox dynamic cycle. The incorporation of indium sulfate effectively improves the contact properties and band energy alignment at the ITO/perovskite interface, ultimately achieving a high‐power conversion efficiency of 22.97%. The device retains 91.6% of its initial efficiency after 1200 h of continuous illumination, providing new insights for the development and application of perovskite solar cells without electron transport layers.