The crystal structure of the perovskite films modified by ionic liquid (ILs) BMIMAc under various annealing durations was characterized by X-ray diffraction.

The difference between the control group and the BMIMAC-modified sample was observed after annealing for a short time (30 seconds). The peak intensity of the perovskite phase in the control group was significantly stronger than that in the BMIMAc modified samples, indicating rapid perovskite phase formation. Upon extending the annealing time to 10 minutes, there was a significant increase in PbI2 content in the control group, while the perovskite phase peak remained relatively stable, suggesting high residual PbI2 content in the final perovskite film. 

The crystal structure and the residual PbI2 of perovskite films can be clearly discerned through X-ray diffraction analysis. These outcomes furnish significant data support for the impact of ILs on the growth kinetics of perovskite crystals and the regulation of the residual PbI2 content in perovskite films.