Discovery of a Ce3+-activated red nitride phosphor for high-brightness solid-state lighting

Abstract

Red-emitting phosphors (usually Eu²⁺-activated) play indispensable roles in manipulating the color rendition and color temperature of InGaN-based solid state lighting, but they usually suffer from luminance saturation under high-power density irradiation and thus are hard to use to fabricate high-brightness lighting sources. Ce³⁺-doped red phosphors with short decay times therefore need to be developed to solve the bottleneck problem. In this work, we proposed an empirical structure criterion for screening Ce³⁺-doped red phosphors and discovered HP-CaSiN₂:Ce³⁺, which has an emission peak at 610 nm, a full-width at half maximum (FWHM) of 160 nm and a quantum efficiency of 40.3% under 450 nm excitation. Under blue laser irradiation (5.47 W), HP-CaSiN₂:Ce³⁺ shows a luminance saturation threshold of 10.89 W mm⁻², luminous flux of 1087 lm and luminous efficacy of 198.7 lm W⁻¹, which are 5.4 and 7.3 times higher than the reported CaAlSiN₃:Eu²⁺ counterparts. In addition, it can also serve as a red component for creating warm white LEDs with an excellent color-rendering index (Ra) of 91.5 and a small chromaticity shift (ΔE: 1.1 × 10⁻²). The discovery of the red-emitting HP-CaSiN₂:Ce³⁺ makes it possible to search for and design long-wavelength Ce³⁺-doped phosphors by the proposed criterion, and paves an avenue for it to be used in high-power solid state lighting.