Limited energy migration and circumscribed multiphonon relaxation produced non-concentration quenching in a novel dazzling red-emitting phosphor

Abstract

White LED applications are still constrained by extremely efficient narrow band red emitting phosphors. Meanwhile, the concentration quenching induced by energy migration is the main reason that limits the emission intensity of a red emitting phosphor. Therefore, developing a novel red emitting material with energy migration limitations seems necessary. Here, we proposed and realized the non-concentration quenching doping of Eu³⁺ ions in a Sr₉Y_2−2xW₄O₂₄:xEu³⁺ (0 ≤ x ≤ 1.0) phosphor for the first time by means of host preferential selection. By clearly investigating the crystal structure and luminescence kinetics, the long-distance between the nearby Eu³⁺ ions and the low phonon energy are the main reasons that suppress the energy migration and the cross-relaxation among Eu³⁺ ions. These advantages result in a high internal (90.47%) and external quantum efficiency (42.1%) of Sr₉Eu₂W₄O₂₄. With the help of the Judd–Ofelt theory and the large value of oscillator strength Ω₂, Eu³⁺ ions are verified to occupy the non-symmetric lattice site with high color purity (94.4%). In addition, only 5.2% emission intensity loss at 140 °C can guarantee its application in LED devices. Moreover, the SYWO:Eu³⁺ phosphor has high thermal tolerance, high color stability, excellent moisture resistance and superior physical/chemical stability, and thus has broad practical spectral application prospects. The prepared WLED shows superior performance, and the calculated NTSC values are as high as 101.8% and 104.7%, respectively. For comparison, the optical performances of the Sr₉Y₂W₄O₂₄:Eu³⁺ phosphor outperform those of the standard commercial red phosphors, Y₂O₃:Eu³⁺ and Y₂O₂S:Eu³⁺, and almost match that of K₂MnF₆. These results may pave the way for fresh approaches to the study of high-performance Eu³⁺-activated phosphors.