Efficient and stable perovskite solar cells with regulated depletion region

Irreversible ion migration from the perovskite layer to the charge transport layer and metal electrodes causes irreversible efficiency loss in perovskite solar cells. Confining the mobile ions within the perovskite layer is a promising strategy to improve the long-term operational stability of solar cells. Here we inhibit the migration of iodide ions out of the perovskite under light illumination by creating a depletion region inside the perovskite layer. Precise control of the doping depth induces an electric field within the perovskite that counteracts ion migration while enhancing carrier separation. Our devices exhibit a certified power conversion efficiency of 24.6% and maintain over 88% of the initial efficiency after 1,920 h of continuous illumination under maximum power point conditions (65 °C in ambient air, following the ISOS-L-2 protocol). The power conversion efficiency returns to more than 94% of its initial value after overnight recovery. When operating under repeated 12 h light on/off cycles for over 10,000 h (solar simulator at 65 °C and ambient air, following the ISOS-LC-2 protocol), the efficiency loss is less than 2%. We expect this method to open up new and effective avenues towards enhancing the long-term stability of high-performance perovskite photovoltaics.