In situ deposition of black α-FAPbI3 films by vacuum flash evaporation for solar cells

Formamidinium lead iodide (FAPbI3) is a promising candidate as the solar cell absorption layer with a suitable band gap of 1.45 eV and excellent optoelectronic properties. In this work, we report a new vacuum flash evaporation method to deposit phase-pure black α-FAPbI3 films in situ on low-temperature substrates without post-annealing, and the area of deposited films can be up to 36 cm2 (6 cm × 6 cm). Besides, the unique relationship between substrate temperature and phases in films is demonstrated for the further development of the method. With the α-FAPbI3 films as the active layer, perovskite solar cells with power conversion efficiency of 12.55% are fabricated.