Spatial Heterogeneity of n-Phases Leads to Different Photophysical Properties in Quasi-Two-Dimensional Methylammonium Lead Bromide Perovskite

Quasi-two-dimensional (2D) perovskites have attracted extraordinary attention for next-generation lighting and displays because of their high color purity and performance. Here, we present the results of an investigation of the distribution of n- phases and their impact on photophysical properties of quasi-2D methylammonium lead bromide perovskite film (q-MPB) where n represents the number of PbBr4 octahedral layers. We find that the emission from the low-n-phase region is blue-shifted compared to the emission from the medium-n-phase and high-n-phase regions. The yield and lifetime of the emission are higher for the medium-n-phase region due to the higher quasi-2D nature of the particles. Temperature-dependent two-photon photoluminescence measurements show that exciton-phonon interaction is stronger for the low-n-phase region, and it decreases when the n-phases increase. Our work demonstrates the impact of spatial heterogeneity of n-phases on light-emission properties, which is of considerable importance for the development of highly efficient next-generation q-MPB-based LEDs.