CH3NH3Br Additive for Enhanced Photovoltaic Performance and Air Stability of Planar Perovskite Solar Cells prepared by Two‐Step Dipping Method

The biggest challenge for the pursuit of potentially available perovskite solar cells (PSCs) is to achieve both high power conversion efficiency and good long‐term stability. Here we report a facile CH3NH3Br (MABr) additive route to achieve the aim. We demonstrate that the application of MABr additive can greatly improve the quality of the perovskite film by diminishing the number of small crystal grains to form large ones, which can substantially decrease grain boundaries and enable direct connection of electron‐ and hole‐transport layers with one large crystal grain. These changes lead to enhanced electron transport rate, suppressed recombination, improved photovoltaic performance, and reduced hysteresis of the device assembled using the perovskite film with MABr additive compared to the device without the MABr additive. Furthermore, the large crystal grains and their compact stacking can effectively withstand moisture corrosion, thereby contributing to significantly enhanced air stability for the perovskite film with MABr additive and the corresponding device. This work highlights the valuable MABr additive route for developing potentially available, efficient, and stable PSCs.