Pressure-Induced Emission toward Harvesting Cold White Light from Warm White Light.

The pressure-induced emission (PIE) behavior of halide perovskites has attracted widespread attention and has potential application in pressure sensing. However, high-pressure reversibility largely inhibits practical applications. Here, we describe the emission enhancement and non-doping control of the color temperature in two-dimensional perovskite (C6 H5 CH2 CH2 NH3 )2 PbCl4 ((PEA)2 PbCl4 ) nanocrystals (NCs) through high-pressure processing. A remarkable 5 times PIE was achieved at a mild pressure of 0.4 GPa, which was highly associated with the enhanced radiative recombination of self-trapped excitons. Of particular importance is the retention of the 1.6 times emission of dense (PEA)2 PbCl4 NCs upon the complete release of pressure, accompanied by a color change from "warm" (4403 K) to "cold" white light with 14295 K. The irreversible pressure-induced structural amorphization, which facilitates the remaining local distortion of inorganic Pb-Cl octahedra with respect to the steric hindrance of organic PEA+ cations, should be greatly responsible for the quenched high-efficiency photoluminescence.