Specific Influences\nof Trap States with Distinct Spatial\nand Energetic Distributions on Ion Migration Dynamics in Metal Halide\nPerovskites

Trap state engineering has been widely employed to manipulate\nthe\ndynamics of ion migration in metal halide perovskites (MHPs), a crucial\nfactor associated with the performance and stability of MHP-based\ndevices. However, the specific roles of different trap states remain\npoorly understood due to their complicated spatial and energetics\ndistributions. Herein, we propose a methodology for independently\nregulating the distributions of bulk shallow and surface deep trap\nstates in MHPs. By combining in situ photoluminescence spectroscopy\nwith wide-field imaging microscopy, we elucidate the effect of surface\ntrap states on promoting long-range interparticle ion migration. Interestingly,\nwe ascertain with time-resolved photoelectric techniques that the\nmajority of mobile ionic defects involved in ion migration are predominantly\ncontributed by bulk trap states. Our findings suggest that targeted\nmanipulation of bulk shallow and surface deep trap states can be effective\nin reducing the number of mobile ions and decelerating the rate of\nion migration, respectively.