Experimental and Theoretical Investigation of Eu 3+ ‐Doped LiTaGeO 5 Red Emitting Phosphors for Solid‐State Lighting

Developing efficient and thermally stable red phosphors is important for high‐performance phosphor‐converted white light‐emitting diodes. Herein, Eu 3+ ‐activated LiTaGeO 5 phosphors were synthesized by a solid‐state reaction and systematically investigated through combined experimental and theoretical approaches. Rietveld refinement and first‐principles calculations suggest that Eu 3+ preferentially occupies the Li site, while electronic structure calculations reveal localized Eu 4 f states without substantially altering the host framework. Under 394 nm excitation, LiTaGeO 5 :Eu 3+ exhibits intense red emission at 611 ( 5 D 0 → 7 F 2 ) together with pronounced deep‐red emission near 704 nm ( 5 D 0 → 7 F 4 ). The optimized LiTaGeO 5 :0.033Eu 3+ phosphor shows a photoluminescence quantum yield of 51.06% and retains approximately 86% of its initial emission intensity at 423 K, and has a thermal‐quenching activation energy of about 0.52 eV. A NUV‐pumped WLED achieves a CRI of 91 and a CCT of 4500 K. Transmission imaging, fluorescent anti‐counterfeiting, infrared thermography, and COMSOL simulations further demonstrate its potential for solid‐state lighting and optical applications.