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

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 (ln₂(SO₄)₃) functional layer at the buried interface of the perovskite. The ln³⁺ exhibits gradient doping at the buried interface, acting as a redox buffer to oxidize Pb⁰ to Pb²⁺, while the generated ln⁺ reduces I⁰ 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.