Enhancing the crystallinity of HC(NH₂)₂PbI₃ film by incorporating methylammonium halide intermediate for efficient and stable perovskite solar cells

For organic-inorganic hybrid perovskite solar cells (PerSCs), the crystallinity and the grain size of the perovskite films are crucial for effective exciton dissociation and charge transportation. Herein, we introduce methylammonium halide (MABr and MACl) intermediates to control the perovskite formation processes via intramolecular exchange. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS) are used to monitor the transition from intermediate to perovskite. It is particularly noteworthy that as Cl^- and MA⁺ are removed from the film as MACl vapor, the intermediate derived from Cl-Hybrid eventually turns into FAPbI₃ perovskite after thermal annealing. The morphology, crystallinity, fluorescence lifetime and the stability of perovskite films derived from different methylammonium halide intermediates are also investigated, and PerSCs based on different perovskite films are fabricated. The PerSCs derived from MACl intermediate exhibit the best photovoltaic performance with a PCE of 19.16%, and the PCE reaches 15.87% for MABr intermediated PerSCs, much higher than that (13.72%) of the control device without methylammonium halide intermediates. Furthermore, MACl intermediated PerSCs demonstrate the best stability due to the highest crystallinity. Our findings indicate that methylammonium halide intermediating is a feasible and effective approach to acquire high crystallinity of perovskite film for high performance and stable PerSCs.