Data-driven discovery of energy materials: efficient BaM2Si3O10 : Eu2+ (M = Sc, Lu) phosphors for application in solid state white lighting

Abstract

In developing phosphors for application in solid state lighting, it is advantageous to target structures from databases with highly condensed polyhedral networks that produce rigid host compounds. Rigidity limits channels for non-radiative decay that will decrease the luminescence quantum yield. BaM₂Si₃O₁₀ (M = Sc, Lu) follows this design criterion and is studied here as an efficient Eu²⁺-based phosphor. M = Sc³⁺ and Lu³⁺ compounds with Eu²⁺ substitution were prepared and characterized using synchrotron X-ray powder diffraction and photoluminescence spectroscopy. Substitution with Eu²⁺ according to Ba_1−xEu_xSc₂Si₃O₁₀ and Ba_1−xEu_xLu₂Si₃O₁₀ results in UV-to-blue and UV-to-blue-green phosphors, respectively. Interestingly, substitution with Eu²⁺ in the Lu³⁺ containing material produces two emission peaks at low temperature and with 365 nm excitation, as allowed by the two substitution sites. The photoluminescence of the Sc³⁺ compound is robust at high temperature, decreasing by only 25% of its room temperature intensity at 503 K, while the Lu-analogue suffers a large drop (75%) from its room temperature intensity. The decrease in emission intensity is explained as stemming from charge transfer quenching due to the short distances separating the luminescent centers on the Lu³⁺ substitution site. The correlation between structure and optical response in these two compounds indicates that even though the structures are three-dimensionally connected, high symmetry is required to prevent structural distortions that could impact photoluminescence.