Zero-thermal-quenching and improved chemical stability of a UCr4C4-type phosphor via crystal site engineering

Europium-doped UCr4C4 cuboid phosphors with narrow and tunable emission show promise for application in designing light-emitting diodes with high color purity and thermal stability. Nevertheless, their poor chemical stability bottlenecks their use in lighting applications. Herein, a dual narrow-band blue-emitting Ce3+-doped CsNa2K(Li3SiO4)4 (CNKLSO) cuboid phosphor with a quantum yield of 80% is synthesized. The dual-band emission is attributed to the occupation of Ce3+ at two distinct sites of CNKLSO, which is consistent with the density functional theory outcomes. Ce3+ doping produces stable emission characteristics, in contrast to Eu2+ incorporation, because of the improved site stability, as realized from bond valence sum calculations. Remarkably, no drop in the emission intensity is observed even at 200 °C, making CNKLSO:Ce3+ the first Ce3+-based zero-thermal-quenching phosphor. A CNKLSO:Ce3+-based white light-emitting diode displays an excellent color rendering index (~95) at a high flux current of 1000 mA. The proposed study indicates that Ce3+ doping in other UCr4C4- type oxide phosphors may improve the site stability, which in turn the chemical stability of the phosphor materials can be boosted.