Temperature dependence of photo-induced phase segregation in bromide-rich mixed halide perovskites

TL;DR

This study investigates how temperature influences the early stages of phase segregation in mixed halide perovskites, revealing temperature-dependent phase transitions and intermediate photoluminescence features crucial for optoelectronic applications.

Contribution

It provides a detailed analysis of temperature effects on anion segregation and phase transitions in mixed halide perovskites during initial stages, using advanced photoluminescence techniques.

Findings

Temperature prolongs initial segregation stages.

Intermediate photoluminescence peaks are observed at low temperatures.

Phase transition from orthorhombic to tetragonal occurs with temperature.

Abstract

Mixed halide perovskites undergo phase segregation, manifested as spectral red-shifting of photoluminescence spectra under illumination. In the iodine-bromide mixed perovskites, the origin of the low-energy luminescence is related to iodine-enriched domains formation. Such domains create favorable bands for the induced carrier funneling into them. Despite the phase segregation process is crucial for mixed halide perovskite-based optoelectronics, numerous gaps exist within the understanding of this phenomenon. One such gap pertains to the emergence of temporary and intermediate photoluminescence peaks during the initial stages of phase segregation. However, these peaks appear only within the first few seconds of illumination. Nevertheless, the decreasing temperature may prolong these initial stages. In this work, we carry out a detailed study of the temperature dependence of anion segregation in MAPbBr_2I and MAPbBr2.5I0.5 halide perovskites, to obtain a deeper comprehension of segregation processes, particularly during their initial stages. The temporal evolution of low-temperature photoluminescence reveals the undergoing of the intermediate stage during the segregation process and temperature-related phase transition from orthorhombic to tetragonal phase. To complement the phase segregation study, the temperature dependence of time-resolved photoluminescence spectroscopy is provided, allowing us to estimate the change in the photoluminescence lifetimes for the initial and segregated peaks with temperature.