Tunable concentration/excitation-dependent deep-red and white light emission in single-phase Eu2+-activated Sc-based oxide phosphors for blue/UV-LEDs

Abstract

Efficiently modulating the site occupation of activators has important implications in the design of color-tunable phosphors. In this paper, we report a series of novel Sr₃Sc₄O₉:xEu phosphors. The activators (Eu²⁺) selectively occupy multiple cationic sites (Sr1–3 and Sc1–4) in the Sr₃Sc₄O₉ matrix with the increase of doping concentration, thus achieving the modulation of emission color from deep-red to white to green. The structure-dependent luminescence mechanism is investigated in detail. The PL spectrum of the Sr₃Sc₄O₉:0.06Eu phosphor upon blue light excitation exhibits an asymmetrically broad deep-red emission band peaking at 688 nm with a FWHM ≈ 100 nm, which clearly overlaps with the absorption curves of red-phytochrome (P_r) and far-red-phytochrome (P_fr). The photoluminescence quantum yield (PLQY) is significantly improved from 2.7% to 19.18% by adopting a double-reduction strategy. The full-visible-spectrum white emission of Sr₃Sc₄O₉:0.01Eu is achieved when excited by UV light. A full-spectrum white LED with R_a = 86 and CCT = 5040 K was packaged with a single-component white emission Sr₃Sc₄O₉:0.01Eu phosphor. All the results suggest the utilization potential of multifunctional Sr₃Sc₄O₉:xEu phosphors in agricultural and full-spectrum general lighting.