Highly luminescent and stable lead-free cesium copper halide perovskite powders for UV-pumped phosphor-converted light-emitting diodes

Lead halide perovskites have drawn extensive attention over recent decades owing to their outstanding photoelectric performances. However, their toxicity and instability are big issues that need to be solved for further commercialization. Herein, we adopt a facile dry ball milling method to synthesize lead-free Cs₃Cu₂X₅ (X = I, Cl) perovskites with photoluminescence (PL) quantum yield up to 60%. The optical features including broad emission spectrum, large Stokes shift, and long PL lifetime can be attributed to self-trapped exciton recombination. The as-synthesized blue emissive Cs₃Cu₂I₅ and green emissive Cs₃Cu₂Cl₅ lead-free perovskite powders have good thermal stability and photostability. Furthermore, UV-pumped phosphor-converted lightemitting diodes were obtained by using Cs3Cu2I5 and Cs3Cu2Cl5 as phosphors.