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

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 MAPbI(3)center dot 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%.