Effect of CH₃NH₃I concentration on the physical properties of solution-processed organometal halide perovskite CH₃NH₃PbI₃

Organic-inorganic halide perovskite CH₃NH₃PbI₃films were synthesized by low-temperature solution method by using a two-step spin-coating technique. We detailedly investigated the effect of the concentration of CH₃NH₃I solution on the morphology and optical properties of CH₃NH₃PbI₃films, and a regular morphology evolution was observed. Further, temperature-dependent photoluminescence measurement was performed, and a structural phase transition of the CH₃NH₃PbI₃films at 150 K was revealed by examining the temperature dependence of the peak positions and widths. In addition, the corresponding exciton binding energy and optical phonon energy of the CH₃NH₃PbI₃films were extracted in the high-temperature tetragonal phase based on the experimental data. It can be anticipated that our results obtained provide valuable information for the understanding on the optical properties of perovskite CH₃NH₃PbI₃, and also their future applications in optoelectronic devices.