Deep-Red (Sr,Ba)Lu2O4: Eu2+ Phosphor for Full-Spectrum Lighting

Abstract

Developing violet-light-excitable deep-red (650∽660 nm) Eu²⁺ activated phosphor is essential for full-spectrum lighting. However, the related phosphors with facile synthesis, excellent optical performance and superior thermal stability are scarce. Herein, we report a new class of (Sr,Ba)Lu₂O₄: Eu²⁺ deep-red phosphor (660 nm) excitable by violet light via Ba²⁺-induced local structure engineering. Impressively, tunable emission from 615 nm to 682 nm, accompanied with significant improvement of thermal stability (81%@423K), is achieved by partially substituting Sr²⁺ by Ba²⁺ in SrLu₂O₄: Eu²⁺. Crystal-field analysis, density functional theory (DFT) calculations and thermoluminescence (TL) spectra confirm that the strong distortion and enhanced covalency of [EuO₆] octahedron are responsible for spectral tunability and the formation of shallow trapping states is beneficial for electron compensation to inhibit thermal quenching in the Sr_0.85Ba_0.15Lu₂O₄: Eu²⁺ phosphor. Finally, a white light-emitting diode (wLED) prototype fabricated by coupling the Sr_0.85Ba_0.15Lu₂O₄: Eu²⁺ deep-red phosphor and commercial blue/green phosphors with violet chip can yield sunlight-like white light with an ultra-high color rendering index (CRI: R_a=95.2, R₉=97.0) and an appropriate correlated color temperature (CCT) of 4121 K, verifying its significant application potential in full-spectrum solid-state lighting.