Redirecting ion migration pathways in MAPbBr₃ via [110]-oriented surface channel patterning as revealed by micro-area...

Ion migration is a critical factor governing the operational stability and optoelectronic performance of metal-halide perovskite devices. Here, we demonstrate a surface channel engineering strategy to modulate ion migration pathways in MAPbBr₃ single crystals by introducing a [110]-oriented channel structure, which effectively redirects ionic flux and mitigates ion accumulation at electrodes. Through comparative electrical characterization along the [100] and [110] crystallographic directions, we reveal that the ionic conductivity along [110] substantially exceeds that along [100], with the ratio of ionic to electronic conductivity reaching approximately 3.3 for the [110] orientation. Micro-area photoluminescence (PL) spectroscopy and time-resolved PL (TRPL) measurements on 10-μm-scale electrode regions before and after electrical polarization demonstrate that ion accumulation locally modulates both PL intensity and carrier lifetime, manifesting as enhanced emission at the anode and quenched emission at the cathode. Furthermore, PL mapping of the surface-engineered channel reveals a distinct intensity gradient along the channel direction, with reduced emission near the anode contact and enhanced emission near the cathode contact, directly evidencing the successful redirection of ion migration from the [100] to the [110] direction. This work provides a viable pathway toward mitigating ion-migration-induced degradation in perovskite optoelectronics through crystallographically selective surface patterning.