Evolution of self-trapped exciton emission tuned by high pressure in 2D all-inorganic cesium lead halide nanosheets

Abstract

Broadband self-trapped exciton (STE) emission in two-dimensional (2D) perovskites has attracted intense attention due to its promising solid-state lighting application. However, few studies have focused on the evolution of structure-optical properties of 2D perovskite nanosheets under pressure tuning. We report a remarkably enhanced broad STE emission in all-inorganic 2D CsPbCl₃ perovskite nanosheets under pressure. Comprehensive research analysis demonstrates that 2D CsPbCl₃ perovskite nanosheets undergo an isostructural transition and then transform into an amorphous state; theoretical calculations confirm this. Pressure-driven broadband emission with significant Stokes shifts caused by increasing the lattice distortion to enhance the exciton–phonon coupling is observed. A remarkable enhancement of STE emission was achieved, which is highly correlated with the distortion of octahedra that effectively enhanced the radiative recombination of STEs. This research enhances the basic understanding of the structure-optical properties of CsPbCl₃ perovskite nanosheets and is expected to promote research on perovskites under high pressures.