Formation of organic–inorganic mixed halide perovskite films by thermal evaporation of PbCl2 and CH3NH3I compounds

Abstract

Organic–inorganic hybrid perovskites were prepared by thermal evaporation from precursor materials PbCl₂ and CH₃NH₃I (MAI). The structures of the perovskite films with various ingredients were characterized by X-ray diffraction (XRD), UV-vis absorption, and scanning electron microscopy (SEM). We found that with the addition of MAI material the evaporated PbCl₂ films were initially transformed to PbI₂, then to standard a stoichiometric perovskite and finally to the MAPbI₃·xMAI phase. The film composition ingredients strongly affect the device performance. An unmatched PbCl₂ to MAI ratio in the evaporated films resulted in reduced conversion efficiency and higher moisture sensitivity. The planar perovskite solar cells with organic charge layers showed negligible photocurrent hysteresis and delivered a power conversion efficiency of 10.5%.