Precise tuning of the thickness and optical properties of highly stable 2D organometal halide perovskite nanosheets through a solvothermal process and its applications as a white LED and a fast photodetector

Precise control of the thickness of large-area 2D organometal halide perovskite layers is extremely challenging owing to the inherent instability of the organic component. Herein, a novel, highly reproducible and facile solvothermal route is reported to synthesize and tailor the thickness and optical bandgap of the organic-inorganic halide perovskite nanosheets (NS). Our study reveals that self-assembly of randomly oriented perovskite nanorods leads to the growth of multilayered perovskite NS at ~100 C, while at higher temperature large area few-layer to bilayer 2D NS (CH3NH3PbBr3) are obtained through lattice expansion and layer separation depending precisely on the temperature. Interestingly, the thickness of the 2D NS shows a linear dependence on the reaction temperature and thus enables precise tuning of the thickness from 14 layers to 2 layers giving rise to a systematic increase in the bandgap and appearance of excitonic absorption bands. Quantitative analysis of the change in the bandgap with thic...