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

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, a new class of (Sr,Ba)Lu2O4: Eu2+ deep‐red phosphor (660 nm) excitable by violet light via Ba2+‐induced local structure engineering is reported. Impressively, tunable emission from 615 to 682 nm, accompanied by significant improvement of thermal stability (81%@423 K), is achieved by partially substituting Sr2+ by Ba2+ in SrLu2O4: Eu2+. Crystal field analysis, density functional theory calculations, and thermoluminescence 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 Sr0.85Ba0.15Lu2O4: Eu2+ phosphor. Finally, a white light‐emitting diode prototype fabricated by coupling of the Sr0.85Ba0.15Lu2O4: 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 (Ra = 95.2, R9 = 97.0) and an appropriate correlated color temperature of 4121 K, verifying its significant application potential in full‐spectrum solid‐state lighting.