Revealing the properties of defects formed by CH_3NH_2 molecules in organic-inorganic hybrid perovskite MAPbBr_3

摘要

The properties of defects in organic-inorganic hybrid perovskite are widely studied from the first-principles calculation. However, the defects of methylamine (methylamine = CH_3NH_2), which would be easily formed during the preparation of the organic-inorganic hybrid perovskite, are rarely investigated. Thermodynamic properties as well as defect states of methylamine embedded MAPbX_3 (MA = methyl-ammonium = CH_3NH_3, X = Br, I) are studied based on first-principles calculations of density functional theory. It was found that there is a shallow defect level near the highest occupied molecular orbital, which induced by the interstitial methylamine defect in MAPbBr_3, will lead to an increase of photoluminescence. The calculation results showed that interstitial defect states of methylamine may move deeper due to the interaction between methylamine molecules and methyl-ammonium cations. It was also showed that the interstitial methylamine defect is stable at room temperature, and the defect can be removed easily by annealing.