Phase‐Transition‐Cycle‐Induced Recrystallization of FAPbI3 Film in An Open Environment Toward Excellent Photodetectors with High Reproducibility

Perovskite is an attractive building block for future optoelectronic applications. However, the strict fabrication conditions of perovskite devices impede the transformation of lab techniques into commercial applications. Here, a facile annealing‐free posttreatment is proposed to reconstruct the perovskite film to obtain high‐performance photodetectors with an optimized production rate. With posttreatment by methylamine thiocyanate, the prefabricated formamidinium‐lead triiodide (FAPbI(3)) film will undergo a recrystallization process consisting of a repeating phase‐transition‐cycle (PTC) between the black and yellow phases of FAPbI(3), which improves the crystal quality and eliminates defects. As a result, some casually prepared or even decomposed perovskite films can be reconstructed, and the dispersion degree of the device performance based on the posttreatment method decreases by ≈21% compared to the traditional antisolvent method. This facile and annealing‐free posttreatment will be an attractive method for the future industrial production of perovskite devices.