Electrical Properties of Inorganic Perovskites CsPbBr₃ Nanosheet Based on Strain Engineering

Fully inorganic CsPbX₃ perovskites have emerged as promising optoelectronic materials because they retain the excellent optoelectronic properties of their hybrid counterparts while offering improved resistance to moisture and heat, although challenges such as soft crystal lattices, high ionic mobility, and easy defect formation remain. Strain engineering provides a novel approach to optimizing the optoelectronic properties of perovskite thin-film devices. This study demonstrates solution-grown CsPbBr₃ nanosheets (12-22 nm thick, ~10 μm lateral size) on ITO substrates. The I-V characteristics of vertical tip/CsPbBr₃/ITO structures were measured under varying compressive loads using conductive AFM, revealing load-dependent behavior. Analysis through thermionic emission modeling demonstrated an inverse correlation between the applied load and Schottky barrier height at the tip-sample interface. Furthermore, piezoresponse force microscopy quantifies thickness-dependent effective piezoelectric coefficients (d33eff = 5.8, 3.7, and 1.2 pm/V for 12, 17.5, and 22 nm nanosheets). Consistent with piezoelectric electronic theory, these results demonstrate piezoelectric-effect-induced Fermi level lowering and consequent Schottky barrier reduction. These findings provide fundamental insights for strain-engineered perovskite optoelectronics.