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

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 beta-Cs3Cu2Cl5 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 degrees 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.