Controlling crystallization temperature and morphology of FAPbI3 thin films via solvent engineering

Perovskite solar cells have emerged as promising candidates for next-generation photovoltaics, yet achieving both high efficiency and long-term durability critically relies on forming high-quality perovskite crystals with enlarged grain sizes. However, these factors remain insufficiently understood and are often explored through trial-and-error approaches. Here, we elucidate the crystallization dynamics of formamidinium lead iodide (FAPbI3) thin films prepared using different solvents via in situ heating GIWAXS with synchrotron radiation. We reveal that the initial δ-phase grain size governs the final perovskite morphology, offering guidelines for scalable fabrication of uniform, large-grained FAPbI3 layers.