Low‐Temperature Atomic Layer Deposition of Double‐Layer Water Vapor Barrier for High Humidity Stable Perovskite Solar Cells

Abstract In recent years, remarkable progress has been made in improving the power conversion efficiency of perovskite solar cells, but their long‐term stability is not so optimistic. In response to this, ion engineering, interface engineering, and encapsulation engineering have been used to enhance the long‐term stability of solar devices. Here, a double‐layer water vapor barrier consisting of SiAl_xO_y buffer layer and SiO₂ vapor isolation layer, prepared by atomic layer deposition under 100 °C, is demonstrated. SiAl_xO_y layer provides sufficient self‐limiting reactive sites for the deposition of SiO₂, so that a more uniform and dense vapor isolation layer can be deposited. This double‐layer water vapor barrier can effectively isolate water vapor to erode the internal functional layers of the perovskite device, prevent ion migration, and improve the long‐term stability of the device. Moreover, the SiAl_xO_y/SiO₂ barrier can be conducive to the transfer of charge between interfaces, and further enhances the conversion efficiency of the device. Overall, compared with the control device, the conversion efficiency of the perovskite device with a double‐layer water vapor barrier is increased from 17.08% to 19.16%, and the long‐term stability is significantly improved, which can maintain 92% efficiency for 2400 h under 35% humidity at room temperature.