Illumination Regulated Ion Migration in Metal Halide Perovskite

Ion migration in CsPbBr₃ perovskites, crucial for device stability and performance, is investigated under combined illumination and direct current (DC) or alternating current (AC) bias using macroelectrical and nanoscale microscopy. DC measurements demonstrate that illumination suppresses bias-induced ion migration, reducing the current drop amplitude (ΔI/I) from 60.68% (dark) to 18.19% (3.80 mW/cm²), attributed to photogenerated carrier passivating vacancies. Photocurrent atomic force microscopy reveals grain boundaries as preferential migration pathways under light, exhibiting 9.6-fold higher mechanical work dissipation than grains. Under AC bias, illumination enhances polarization, evidenced by an +8° out-of-plane phase shift in piezoresponse force microscopy, and increases surface potential (Kelvin probe force microscopy: 2.35 V dark to 3.27 V), confirming light-promoted ion migration via polarization modulation. These findings elucidate the mechanism of light-regulated ion migration in CsPbBr₃, facilitating optimization of the perovskite device stability and performance.