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

Organic-inorganic halide perovskite CH3NH3PbI3 films 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 CH3NH3PbI3 films, and a regular morphology evolution was observed. Further, temperature-dependent photoluminescence measurement was performed, and a structural phase transition of the CH3NH3PbI3 films 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 CH3NH3PbI3 films 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. •A regular morphology evolution was observed by adjusting CH3NH3I concentration.•A tetragonal-to-orthorhombic phase transition was observed in CH3NH3PbI3.•The critical transition temperature is about 150 K.•The exciton binding energy of CH3NH3PbI3 was extracted to be ∼83.2 ± 14.5 meV.