Phase evolution and fluorescence stability of CsPb2Br5 microwires and their application in stable and sensitive photodetectors

Abstract

As a special two-dimensional layered perovskite material, CsPb₂Br₅ has attracted great attention and shows great stability and excellent photoelectric performance. Herein, a simple and environment-friendly two-step method was used to prepare CsPb₂Br₅ microwires. The effect of substrate temperature on the growth process of the microwires was investigated. With the increase in substrate temperature, the amount of nucleation in the microwire increased, and the length of the microwire decreased from several millimeters to dozens of microns. A parasitic phase of CsPbBr₃ was found in CsPb₂Br₅ through synchrotron radiation wide-angle X-ray scattering (WAXS). The in situ heating test of WAXS results showed that the CsPb₂Br₅ microwire had good structure thermostability, and no phase transformations were observed when the temperature increased to 350 °C before the thermal decomposition of CsPb₂Br₅. Spatial and temporal resolved fluorescence measurements reveal the distribution of defect states and carrier recombination processes in different regions of the microwires. The changes in fluorescence characteristics affected by annealing temperature suggested the evolution of defect states and components in the CsPb₂Br₅ microwires at different temperatures. A photodetector (PD) based on CsPb₂Br₅ microwires exhibits an “on/off” current ratio of 800, a short rise time of 43 ms and a decay time of 83 ms. After being placed in air without any package for 90 days, the photocurrent of the PD is still maintained at 82% of its initial value.