The band gap energy of lead mixed bromide-iodide perovskite can be simply tuned by adjusting the ratio between the composing halide anions, which would be segregated again upon continuous light illumination to form the iodide-rich domains. Here, we have employed transient absorption microscopy to investigate the carrier diffusion dynamics in an individual CsPbBr1.5I1.5 microplate under the influence of such iodide-rich domains. As expected in the phase-segregated microplate, the lifetime of charge carriers is shortened owing to their migration into the iodide-rich domains with a low band gap energy. Surprisingly, the diffusion coefficient of charge carriers is significantly increased in the phase-segregated microplate, signifying their effective acceleration by the iodide-rich domains according to our Green's function simulations. The above findings have advanced the understanding of the carrier diffusion dynamics in mixed-halide perovskites, which would facilitate their potential applications in various optoelectronic devices such as solar cells and photodetectors.
Keywords: carrier diffusion length; carrier transport; mixed-halide perovskite; phase segregation; transient absorption microscopy.