Competitive Site Occupation toward Improved Quantum Efficiency of SrLaScO4:Eu Red Phosphors for Warm White LEDs

The discovery of Eu 2+ -doped high-efficiency red phosphors remains a vital challenge for white light-emitting diode (WLED) applications. It is therefore urgent to find effective strategies managing the oxidation state to help reduce Eu 3+ to Eu 2+ and accordingly increase the photoluminescence quantum yield (PLQY). Herein, a new red-emitting SrLaScO 4 :Eu phosphor is designed, and the PLQY is enhanced from 13% to 67% under 450 nm excitation by employing (NH 4 ) 2 SO 4 -assisted sintering. Combined structural analysis, optical spectroscopy, and theoretical calculation reveal that predominant Eu 2+ prefers to occupy the Sr 2+ sites in the SrLaScO 4 enabling red emission, and a competitive site occupation of Eu 3+ in La 3+ can be restrained, and the reduction mechanism of Eu 3+ to Eu 2+ originating from the (NH 4 ) 2 SO 4 addition is analyzed. The fabricated WLED device using red-emitting SrLaScO 4 :Eu and yellow-emitting Y 3 (Al,Ga) 5 O 12 :Ce 3+ exhibits a high color-rendering index of 86.7 at a low correlated color temperature of 4005 K. This work provides a feasible reduction strategy for guiding the development of high-efficiency Eu 2+ -doped red phosphor for WLED applications.