Preparations of Organo-Lead Halide Perovskite Layers in Humid Air Atmosphere and their Characteristics

In recent years, solar cells based on organometal halide perovskite (hybrid perovskite) materials have emerged as promising low-cost solar cells. These types of solar cells exhibit remarkable high power conversion efficiencies while offering a significant advantage on the simplicity of their fabrications. The formation of organo-metal halide perovskite layer, however, is very sensitive to some process parameters such as concentration, temperature, and humidity. Here, we report the preparation of this perovskite crystal layer of CH₃NH₃PbI₃ (MAPbI₃) under relatively humid air atmosphere, which is a common condition in tropical countries, and understanding its effect on the resulted perovskite layer characteristics. We found that the humidity leads to the formation of a black color layer on the top of dark brown color perovskite layer. This black color layer caused the appearance of optical absorption tail extending to the near infrared region and showed poor x-ray diffraction (XRD) pattern. It also leads to poorer solar cell characteristics. The formation of this layer can be prevented by applying fast deposition-crystallization process with proper solvent and dropping time. (paper)