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

Zhiyu Yang,Gaochao Liu,Yifei Zhao,Yayun Zhou,Jianwei Qiao,Maxim S. Molokeev,Hendrik C. Swart,Zhiguo Xia// ADVANCED OPTICAL MATERIALS//

The discovery of Eu2+-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 Eu3+ to Eu2+ and accordingly increase the photoluminescence quantum yield (PLQY). Herein, a new red-emitting SrLaScO4:Eu phosphor is designed, and the PLQY is enhanced from 13% to 67% under 450 nm excitation by employing (NH4)2SO4-assisted sintering. Combined structural analysis, optical spectroscopy, and theoretical calculation reveal that predominant Eu2+ prefers to occupy the Sr2+ sites in the SrLaScO4 enabling red emission, and a competitive site occupation of Eu3+ in La3+ can be restrained, and the reduction mechanism of Eu3+ to Eu2+ originating from the (NH4)2SO4 addition is analyzed. The fabricated WLED device using red-emitting SrLaScO4:Eu and yellow-emitting Y3(Al,Ga)5O12:Ce3+ 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 Eu2+-doped red phosphor for WLED applications.