Crystal structure and electron transition underlying photoluminescence of methylammonium lead bromide perovskites

Abstract

Bromine-based methylammonium lead hybrid perovskites (CH₃NH₃PbBr₃ or MAPbBr₃) have exhibited remarkable charge transport and optical properties. Nonetheless, the photoluminescence (PL) behavior and electronic transition state are still obscure. In this paper, the intrinsic emission mechanisms of two peaked CH₃NH₃PbBr₃ microcuboid crystals have been investigated. A systematic analysis of the stable-state, transient-state and temperature-dependent spectra demonstrated the structure–activity relationship between optical properties and crystal phase. The lattice symmetry was also confirmed by the two-photon absorption induced PL. The findings can be assigned to the fact that the two emission states with band-energy ∼2.22 eV and ∼2.31 eV are originated from free exciton and free carrier recombination which are attributed to the coexistence of a non-centrosymmetric tetragonal phase and a centrosymmetric cubic phase for CH₃NH₃PbBr₃ microcrystals at higher temperature (>160 K).