Improved Luminescence Performance for W-LED Applications of the Eu3+-Activated Double Molybdate Red Phosphor NaLu(MoO4)2

In this study, a series of novel Eu³⁺-activated NaLu(MoO₄)₂ (NLMO) red phosphors were synthesized for the first time using hydrothermal, sol–gel, and microemulsion methods with varying active agents. The properties of these phosphors, including phase purity, crystal structure, DFT calculations, morphology, luminescence characteristics, thermal stability, and internal quantum efficiency, were comprehensively characterized. The results indicate that the ethylenediaminetetraacetic acid disodium salt (EDTA-2Na)-assisted hydrothermal method is the most suitable approach for the preparation of the phosphor. This method yields phosphors with a regular morphology, outstanding luminescence performance, relatively good thermal stability, and significantly high internal quantum efficiency. The internal quantum efficiency reaches 96.45%, and the phosphor exhibits good thermal stability, with the emission intensity at 423 K remaining about 73% compared to the initial temperature. The CIE chromaticity coordinate of the NLMO/0.13Eu³⁺ sample (0.667, 0.333) is very close to the standard chromaticity coordinate value (0.670, 0.330) from the National Television Standards Committee (NTSC). Remarkably, the color purity of the NLMO:0.13Eu³⁺ phosphor is an impressive 97%. Furthermore, Tb³⁺ was cointroduced in the NLMO:0.13Eu³⁺ phosphor, and its positive effects are discussed. Ultimately, a warm white light-emitting diode (W-LED) was fabricated using the studied NLMO:0.13Eu³⁺ phosphor with a 394 nm near-ultraviolet-emitting LED chip as the excitation source. The W-LED exhibits excellent properties such as high color purity, excellent correlation color temperature, and high color rendering index. Considering all of the results, the NLMO/Eu³⁺ red phosphor obtained by the EDTA-2Na-assisted hydrothermal method is an ideal red component for W-LEDs in various lighting applications.