Specific Influences of Trap States with Distinct Spatial and Energetic Distributions on Ion Migration Dynamics in Metal Halide Perovskites

Trap state engineering has been widely employed to manipulate the dynamics of ion migration in metal halide perovskites (MHPs), a crucial factor associated with the performance and stability of MHP-based devices. However, the specific roles of different trap states remain poorly understood due to their complicated spatial and energetics distributions. Herein, we propose a methodology for independently regulating the distributions of bulk shallow and surface deep trap states in MHPs. By combining in situ photoluminescence spectroscopy with wide-field imaging microscopy, we elucidate the effect of surface trap states on promoting long-range interparticle ion migration. Interestingly, we ascertain with time-resolved photoelectric techniques that the majority of mobile ionic defects involved in ion migration are predominantly contributed by bulk trap states. Our findings suggest that targeted manipulation of bulk shallow and surface deep trap states can be effective in reducing the number of mobile ions and decelerating the rate of ion migration, respectively.