A Lead‐Free All‐Inorganic Metal Halide with Near‐Unity Green Luminescence

Abstract As the increasing demand of lighting display technology, environmentally‐friendly, economic light‐emitting materials with high performance are required. Herein, a novel solution‐processed, highly emissive copper chloride compound β‐Cs 3 Cu 2 Cl 5 is reported. The crystal structure determined by the Rietveld refinement of the powder X‐ray diffraction patterns shows that the corner‐sharing tetrahedral Cu–Cl chains are surrounded by Cs + cations, yielding a one‐dimensional structure at molecular level. The all‐inorganic compound shows excellent photostability, and is thermally stable up to 550 °C. Excitingly, it exhibits room‐temperature photoluminescence in the green region with near‐unity quantum yield. Currently, this appears to be the most efficient lead‐free all‐inorganic green‐light emitting metal halides reported. This work presents a new direction toward the design of high‐efficiency, economic, and environmentally‐friendly light‐emitting materials.