Pressure‐Induced Emission toward Harvesting Cold White Light from Warm White Light

Abstract 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 (C 6 H 5 CH 2 CH 2 NH 3 ) 2 PbCl 4 ((PEA) 2 PbCl 4 ) 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 PbCl 4 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.