Double-scheelite Gd2GeWO8:Eu3+ phosphors with high thermal stability and color purity for plant-cultivation LEDs, WLEDs, personal identification, and anti-counterfeiting

Double-scheelite-structured red-emitting phosphors Gd 2 GeWO 8 (GGWO): x Eu 3+ ( x  = 0 mol%-80 mol%) were synthesized via high-temperature calcination. Under 394 nm excitation, the GGWO:Eu 3+ phosphors presented four prominent emission bands, with the strongest peak located at 615 nm ascribed to the 5 D 0 → 7 F 2 electric dipole transition of Eu 3+ ions. Luminescence and lifetime analyses showed that nearest-neighbor ion interactions induced concentration quenching. The optimal doping concentration was 50 mol%. Based on Judd-Ofelt theory, the intensity parameters ( Ω 2  = 6.39 × 10 −20  m 2 , Ω 4  = 3.83 × 10 −20  m 2 ) were systematically calculated, revealing the asymmetric coordination environment and covalent nature of Eu 3+ ions within the GGWO host. The GGWO:50 mol%Eu 3+ phosphor showed remarkable thermal stability, exhibiting an activation energy of 0.336 eV and 90.38% luminescence intensity retained at 480 K. Its internal quantum efficiency reached 66.23%. All prepared phosphors possessed high color purity above 99.9%. The emission of the red LED fabricated with GGWO:50 mol%Eu 3+ phosphor overlapped well with the absorption spectra of typical plant photosynthetic pigments. Meanwhile, the fabricated white light-emitting diodes (WLEDs) achieved an excellent color rendering index of R a  = 89, with CIE chromaticity coordinates (0.328, 0.324). Oleic acid (OA) modification effectively maintained luminescence performance and distinctly enhanced the resolution and contrast for latent fingerprint (LFP) and lip print imaging. The phosphors also exhibited potential performance in anti-counterfeiting inks. Benefiting from its versatile performance in plant-cultivation LEDs, WLEDs, personal identification, and anti-counterfeiting inks, this red-emitting phosphor can be regarded as a prospective candidate for numerous advanced optical applications.