Crystallization and defects regulation of efficient perovskite solar cells via surface induced secondary grain growth with formamidine iodine treatment

Trap-mediated non-radiative loss is a major efficiency and stability obstale for solution-processed perovskite solar cells (PSCs). To address this issue, defect passivation using organic molecules has been identified as an effective strategy due to the ionic nature of the perovskite lattice. Herein, Ostwald ripening by using formamidine iodine (FAI) is reported to inhibit the carrier trap induced recombination via promoting secondary grain growth at perovskite surface. Based on secondary grain growth with FAI treatment, the graded passivation was presented caused by FA+ and I- from FAI. Moreover, the findings from time resolved photoluminescence and space charge-limited current technology indicate enhancements in the crystal quality. Consequently, this approach yielded a remarkable power conversion efficiency (PCE) of 20.62% for the FAI modified MAPbI3 photovoltaics, with significantly improved open-circuit voltage ratio of 3.10%, short-circuit density ratio of 6.11%, fill factor ratio of 9.46% and PCE ratio of 19.06%. Moreover, the device show the excellent stability. This study introduces simple and reproducible procedures for fabricating PSCs, which can be readily extended to diverse optoelectronic device applications.