Achieving Highly Efficient Warm‐White Light Emission in All‐Inorganic Copper‐Silver Halides via Structural Regulation

Abstract Single‐component metal halides with white light emission are highly attractive for solid‐state lighting applications, but it is still challenging to develop all‐inorganic lead‐free metal halides with high white‐light emission efficiency. Herein, by rationally introducing silver (Ag) into zero‐dimensional (0D) Cs 3 Cu 2 Br 5 as new structural building unit, a one‐dimensional (1D) bimetallic halide Cs 6 Cu 3 AgBr 10 is designed that emits strong warm‐white light with an impressive photoluminescence quantum yield (PLQY) of 94.5% and excellent stability. This structural transformation lowers the conduction band minimum while maintaining the localized nature of the valence band maximum, which is crucial in expanding the excitation spectrum and obtaining efficient self‐trapped excitons (STEs) emission simultaneously. Detailed spectroscopy studies reveal that the white‐light originates from triplet STEs emission, which can be remarkably improved by weakening the strong electron‐phonon coupling and thus suppressing phonon‐induced non‐radiative processes. Moreover, the interesting temperature‐dependent emission behavior, together with self‐absorption‐free property, make Cs 6 Cu 3 AgBr 10 as sensitive luminescent thermometer and high‐performance X‐ray scintillator, respectively. These findings demonstrate a general approach to achieving effective single‐component white‐light emitters based on lead‐free, all‐inorganic metal halides, thereby opening up a new avenue to explore their versatile applications such as lighting, temperature detection and X‐ray imaging.