A novel thermally-stable red phosphor Ba6La2Ga4O15:Eu3+ for WLEDs, anti-counterfeit inks, and fingerprint analysis

Abstract

This work reports the characterization of Ba₆La₂Ga₄O₁₅:Eu³⁺ (BLGO:Eu³⁺), a new Eu³⁺ doped red luminescent phosphor prepared in a high-temperature solid-state reaction. The material was comprehensively characterized, including investigations of its structural features, morphological characteristics, photoluminescence behavior, and potential applications. The samples were systematically characterized by X-ray diffraction and electron microanalysis, and the Eu³⁺ ions effectively replaced the La³⁺ sites in the matrix, and the samples had uniform elemental distributions and high purity. Under 394 and 468 nm excitation, the phosphor exhibits strong red-light emission dominated by 590 nm (⁵D₀ → ⁷F₂ transition) with a color purity close to 100 %. The fluorescent intensity peaked when the doping concentration x = 0.9, and the luminous thermal stability was excellent (luminescence intensity retention at 473 K was 87.6 % and 83.1 %, respectively). The narrowing of the band gap (3.378 eV) and the electron-leaping mechanism after doping are revealed by density-functional theory calculations. The high-performance warm white Light-emitting diode device was successfully prepared by compounding this phosphor with commercially available blue-green fluorescent materials under 395 nm near-ultraviolet excitation. The test data show that the device exhibits excellent luminescence characteristics: the chromaticity coordinates are (0.3914, 0.3882), which corresponds to a comfortable warm color temperature of 3803 K, and the Color Rendering Index value is 87.6. In addition, when the phosphor is dispersed in a polyvinyl alcohol solution, it emits bright red fluorescence under near-ultraviolet excitation, demonstrating potential for application in the field of anti-counterfeit inks.

Although the quantum efficiency (21.31 %) still needs to be improved, BLGO:Eu³⁺ phosphor has a promising application in White light-emitting diodes (WLEDs), fingerprint analysis and anti-counterfeiting.