A promising thermally robust blue-green Li-α-sialon:Ce3+ for ultraviolet LED-driven white LEDs

Abstract

Rare earth ions doped (oxy)nitride phosphors have been shown great potentials for the use as down-conversion luminescent materials in white light-emitting diodes (wLEDs). To realize super-high color rendering and high efficiency wLEDs driven by a 405 nm LED chip, a blue-green phosphor with high thermal stability and quantum efficiency is required. In this work, we reported an interesting blue-green emitting Li-α-sialon:Ce3+ (LimSi12-m-nAlm+nOnN16-n:Ce3+) that has a high external quantum efficiency of 53.5% and a small luminescence intensity reduction of 6.1% at 423 K. A variety of analytic techniques, such as X-ray diffraction (XRD), photoluminescence (PL) spectra, X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) spectra, were used to clarify the relation between photoluminescent properties and local coordination environments. It showed that the emission color and luminescence intensity of Li-α-sialon:Ce3+ could be controlled by the microstructure tailoring. A warm wLED was demonstrated by pumping the phosphor with the blend of Li-α-sialon:Ce3+, β-sialon:Ce3+ and CaAlSiN3:Eu2+ by a 405 nm LED chip, which has the color temperature, color rendering index and luminous efficacy of 2390 K, 92.2 and 26.05 lm/W under a driven current of 20 mA. Our results indicate that Li-α-sialon:Ce3+ is a promising thermally robust blue-green phosphor for ultraviolet LED-driven wLEDs.