The Phase Inhomogeneity Induced Spatial and Temporal Charge Carrier Transport in Mix-Halide Perovskite

Halide phase segregation in mixed-halide perovskites constitutes a critical challenge limiting the performance and stability of related optoelectronic devices. Conventional macroscopic characterization techniques often fall short in revealing the true impact of phase segregation on charge carrier dynamics. In this study, by integrating optical pump–terahertz probe (OPTP) spectroscopy with spatially resolved pump–probe transient reflectivity microscopy, we directly visualize—for the first time in spatiotemporal dimensions—the non-equilibrium charge transport processes in phase-segregated systems. Our results show that, although phase segregation does not significantly alter the macroscopic charge carrier mobility or the average recombination lifetime, it triggers a rapid “charge funneling” effect at the micrometer scale: photogenerated carriers directionally accumulate into iodine-rich (I-rich) domains within picoseconds, forming localized reservoirs with exceptionally high density and prolonged lifetime. This process is accompanied by a marked enhancement in localized scattering. This work elucidates that the influence of phase segregation on device performance stems primarily from the induced spatial redistribution of carriers and the modulation of local dynamics, rather than from a degradation of bulk transport properties. These findings provide a crucial kinetic perspective for understanding and optimizing phase-segregated mixed-halide perovskite systems.