Ternary solid solution phosphors Ca1-x-yLixAl1-x-ySi1+x+yN3-yOy:Ce3+ with enhanced thermal stability for high-power laser lighting

Abstract

The discovery of thermally robust phosphors is essential to achieve efficient and stable luminescence in solid-state lighting devices, especial in high-power devices. Here, a novel ternary solid solution phosphor enabling to address this challenge is designed by introducing isostructural LiSi2N3 and Si2N2O into CaAlSiN3 lattice. The compound, Ca1-x-yLixAl1-x-ySi1+x+yN3-yOy:Ce3+ (CALSON:Ce), exhibits an excellent thermal stability with an integrated emission loss of only 9% at 200 °C, far smaller than that of the parent CaAlSiN3:Ce3+ (25%). The enhanced thermal stability is assigned to the broadened band gap (5.21 → 5.50 eV) upon the formation of solid solutions. Moreover, the new phosphor presents a broadband (full width at half maximum of 135 nm) yellow-orange emission peaking at 580 nm and shows a high external quantum efficiency of 41.5%. The excellent photoluminescence properties and thermal stability of CALSON:Ce thus enable it to be used under high-power laser excitation, and to produce high-brightness white light having a luminous flux of 392 lm (luminous emittance of 781 lm mm−2), a low correlated color temperature of 4349 K, and a high color rendering index of 70. This work suggests that creating multi-component solid solutions would be a general strategy for designing novel phosphors.