UV Mediated Thickness Control of Colloidal Blue-Emitting 2D CsPbBr₃ Nanoplatelets

The main challenge in the colloidal synthesis of 2D RP halide perovskite nanoplatelets (NPLs) is the uncontrolled formation of NPLs with varying thicknesses due to competitive crystallization rates. In this study, we present a simple UV-assisted method to achieve controlled and stepwise thickness tuning of CsPbBr 3 NPLs, ranging from n = 3–6, under 365 nm irradiation at ambient conditions. NPLs with specific thicknesses display sharp, well-defined absorption and photoluminescence characteristics. This transformation can be halted at any desired stage by simply stopping the UV-exposure. Our findings emphasize the crucial role of surface defects in influencing this transformation.