Effects of Mixed Halide Ions Incorporation on CH3NH3Pb(I,Br)3-x(SCN)x Perovskite Films via Solution Deposition Route

Abstract

Nowadays, a novel solar cell based on an organolead halide perovskite structure, CH3NH3PbX3 (X is a halogen), has been gained a great attraction due to its promising photovoltaic performance. However, their humidity limitation is a serious drawback, which limits practical application of perovskite-based solar cells. In this study, we investigated the improvement of humidity stability and the influence of halide radicals (I- and Br-) on optical and physical properties of thiocyanic-modified CH3NH3PbX3 or CH3NH3PbX3-x(SCN)x films, prepared by two-step deposition method. The mixtures of CH3NH3I and CH3NH3Br solution with different molar ratios were prepared to control the I-:Br- ratios in perovskite films. The characterization of perovskite films was tested by XRD, UV-Vis spectrophotometer, UV-Vis DRS spectroscopy, FE-SEM, and moisture stability testing under constant relative humidity. The results showed that different molar ratios of I- and Br- could strongly affect the properties of perovskite films. The larger amount of Br- promoted the complete reaction of perovskite, larger energy band gap, and higher moisture stability. However, the prepared films were likely to exhibit phase separation due to the formation of iodide-rich and bromide-rich domains.