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

Abstract

• CsNa 2 K(Li 3 SiO 4 ) 4 :Ce 3+ phosphor was synthesized with 80% quantum efficiency. • First zero-thermal-quenching phosphor among other Ce 3+ -doped phosphors. • Upon Ce 3+ doping in host shows excellent chemical stability than Eu 2+ doping. • CsNa 2 K(Li 3 SiO 4 ) 4 :Ce 3+ shows high color rendering index value of 95 at 1000 mA. Europium-doped UCr 4 C 4 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 Ce 3+ -doped CsNa 2 K(Li 3 SiO 4 ) 4 (CNKLSO) cuboid phosphor with a quantum yield of 80% is synthesized. The dual-band emission is attributed to the occupation of Ce 3+ at two distinct sites of CNKLSO, which is consistent with the density functional theory outcomes. Ce 3+ doping produces stable emission characteristics, in contrast to Eu 2+ 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:Ce 3+ the first Ce 3+ -based zero-thermal-quenching phosphor. A CNKLSO:Ce 3+ -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 Ce 3+ doping in other UCr 4 C 4 - type oxide phosphors may improve the site stability, which in turn the chemical stability of the phosphor materials can be boosted.