Study on the correlations between the structure and photoelectric properties of CH3NH3PbI3 perovskite light-harvesting material

The [PbI6] inorganic framework in the CH3NH3PbI3 could be affected by the oxidization effect of I− ions in atmosphere. The [PbI6] octahedral torsion angle increased ∼4.94° after the newly prepared CH3NH3PbI3 powders were stored in dry atmosphere for 30 days at 20 °C according to the results of XRD Rietveld refinement and X-ray Absorption Fine Structure. Analyses based on density of states indicated that UV-vis adsorption edge at ∼850 cm-1 corresponded to electron transition from I-5p orbitals to empty Pb-6p orbitals. The increased [PbI6] octahedral torsion angle made the band gap energy of CH3NH3PbI3 increased according to First-principle calculation and UV-vis absorption spectra. As a result, the band gap energy of CH3NH3PbI3 were strongly related to the structure of [PbI6] inorganic framework because the electrons diffused along the [PbI6] octahedral chains in CH3NH3PbI3 perovskite.