Optical properties of CH3NH3PbI3 crystal grown using inverse temperature crystallization

Perovskite CH₃NH₃PbI₃ (MAPbI₃) single crystal was grown using inverse temperature crystallization method. Crystallinity of the perovskite was confirmed by X-ray diffraction. Photoluminescence (PL) spectra revealed abnormal behavior due to a temperature-induced orthorhombic to the tetragonal phase transition. Four PL emission peaks, A, B, C, and D, were observed in the low temperature regime. Peaks A and B were observed at 756 and 776?nm?at 12?K, and were blue-shifted and disappeared at 130 and 70?K, respectively. Peaks C and D were observed at 789 and 807?nm?at 40?K and were also blue-shifted to 780 and 794?nm?at 100?K. On the other hand, the peak C red-shifted to 799?nm from 100 to 140?K because of an orthorhombic to the tetragonal phase change and was also blue-shifted above 140?K. From the excitation intensity- and temperature-dependent PL results, peaks A and B were assigned to the free-exciton and bound-exciton of the orthorhombic phase crystal, respectively. In addition, peaks C and D were associated with the free-exciton and bound-exciton of the tetragonal phase crystal, respectively. The activation energy of peak C was calculated to be 98?meV from temperature dependence of the PL intensity.