Hybrid Vapor-Solution Sequentially Deposited Mixed-Halide Perovskite Solar Cells

The recent sky-rocketing performance of perovskite solar cells has triggered a strong interest in further upgrading the fabrication techniques to meet the scalability requirements of the photovoltaic industry. The integration of vapor deposition into the solution process in a sequential fashion can boost the uniformity and reproducibility of the perovskite solar cells. In addition, mixed-halide perovskites have exhibited outstanding crystallinity and higher stability compared with iodide-only perovskite. An extensive study was carried out to identify a reproducible process leading to highly crystalline perovskite films that, when integrated into solar cells, exhibited a high power conversion efficiency (max. 19.8%). This was achieved by optimizing the deposition rate of the PbI2 layer and by inserting small amounts of methylammonium (MA) bromide and chloride salts to the primary MAI salt in the solution-based conversion step. The optimum MABr/MAI molar ratio leading to the most efficient and stable solar cells was found to be 0.4. Stabilities were in excess of 90 h for p-i-n type solar cells. This reproducible approach toward the fabrication of triple halide perovskites using a hybrid vapor-solution method is a promising method toward scalable production techniques.