Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3 CH3NH3PbI3

Optical absorption and magnetoabsorption spectra of the lead-halide-based perovskite-type crystals, CH3NH3PbX3 (X=Br, I) have been investigated. The lowest-energy excitons in these crystals are normal three-dimensional Wannier-type excitons. Bohr radii, binding energies, reduced masses, effective g factors, and oscillator strengths of the excitons have been determined with satisfactory accuracy. A larger bandgap and more tightly bound nature of the excitons in CH3NH3PbBr3 compared to those in CH3NH3PbI3 are a natural consequence of the halogen substitution.