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

Developing violet‐light‐excitable deep‐red (650–660 nm) Eu 2+ ‐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)Lu 2 O 4 : Eu 2+ deep‐red phosphor (660 nm) excitable by violet light via Ba 2+ ‐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 Sr 2+ by Ba 2+ in SrLu 2 O 4 : Eu 2+ . Crystal field analysis, density functional theory calculations, and thermoluminescence spectra confirm that the strong distortion and enhanced covalency of [EuO 6 ] 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 0.85 Ba 0.15 Lu 2 O 4 : Eu 2+ phosphor. Finally, a white light‐emitting diode prototype fabricated by coupling of the Sr 0.85 Ba 0.15 Lu 2 O 4 : Eu 2+ deep‐red phosphor and commercial blue/green phosphors with violet chip can yield sunlight‐like white light with an ultra‐high color rendering index ( R a = 95.2, R 9 = 97.0) and an appropriate correlated color temperature of 4121 K, verifying its significant application potential in full‐spectrum solid‐state lighting.