Efficient White Light-Emitting Diodes Based on Cu(I) Activated Single-Phase Halide Single Crystals

Single-phase white light emitters have become a potential substitute for tricolor phosphor mixtures for the white light-emitting diodes (WLEDs) application to simplify device structure and eliminate self-absorption. Newly developed low-dimensional halides, noted for their highly efficient luminescent characteristics, have seen increasing interest in recent years. Herein, highly efficient white-light emission is demonstrated in single-phase zero-dimensional halide single crystal, namely monovalent Cu-doped Cs2HfCl6. Cs2HfCl6:Cu single crystals have three luminescent centers. Two emission peaks at 365 nm and 380 nm correspond to the intrinsic self-trapped excitons emission and a defect-related trapped exciton emission, respectively. Cu doping introduces an intense Cu-bound exciton emission peaking at 540 nm with a large Stokes shift of 250 nm and a high photoluminescence quantum yield of 68%. With different excitation wavelengths and Cu-doping concentrations, Cs2HfCl6:Cu single crystals show tunable emissions. Under 254 nm ultraviolet light excitation, Cs2HfCl6:0.5%Cu yields cold white light with a high color rendering index (Ra = 87.3). These findings demonstrate the potential of Cs2HfCl6:Cu as a promising phosphor for cold WLEDs. This work reports a single-phase zero-dimensional Cs2HfCl6:Cu single crystal for white light-emitting diodes application. Cu doping introduces an intense Cu-bound exciton emission with a high photoluminescence quantum yield of 68%. Cs2HfCl6:0.5%Cu yields efficient cold white light with a high color rendering index (Ra = 87.3).image (c) 2024 WILEY-VCH GmbH