In Situ Methylammonium Chloride-Assisted Perovskite Crystallization Strategy for High-Performance Solar Cells

The optimization of perovskite crystallization is critical to achieving high-performance perovskite solar cells (PSCs). In the standard crystallization methods, the additives play an important role not only in optimizing the crystallization but also passivating the defect states of perovskite films. Methylammonium chloride (MACl) is one of the frequently used additives in this regard. However, the performance mechanism of MACl in the perovskite crystallization process still needs more investigation. This work presents the quality improvement of a perovskite film using MACl vapor as an external chlorine source. The in situ 2D-GIXRD and real-time X-ray diffraction characterizations provide a better understanding the performance mechanism of MACl. Our results demonstrate that exposing the perovskite film to the MACl vapor during the crystallization process can effectively enhance the film quality in addition to enlarging the grain sizes. As a result, the MAPbI3 film optimized by our process leads to highly efficient PSCs with a power conversion efficiency (PCE) of ∼21%.