Top-Down or Bottom-up? Growth direction of gas flow-assisted perovskite layers

Abstract Photovoltaic devices based on metal halide perovskites have been established as a leading technology for future energetic applications, making scalabledeposition methods, compatible with high-throughput yields, more relevant than ever before. However, the key to producing highly efficient devices is to control the film formation process to create homogeneous pinhole-free films. This process becomes more challenging as the active area of the device increases. Our work provides insights into the crystallization dynamics of metal halide perovskite thin films by in-situ monitoring. By utilizing photoluminescence and X-ray diffraction techniques, we identified that the film quality strongly depends on the dynamics of the gas flowing in the drying chamber. Optical and structural in-situ measurements revealed the growth of the perovskite films from bottom to top using a gas-assisted vacuum drying method. These results emphasize the importance of controlling the quenching stream of gases used to crystallize the films after deposition. Furthermore, it establishes a clear development path for future large area perovskite solar cells.