High quantum efficiency and excellent color purity of red-emitting Eu³⁺-heavily doped Gd(BO₂)₃-Y₃BO₆-GdBO₃ phosphors for NUV-pumped WLED applications

Eu³⁺-doped phosphors have been much attractive owing to their narrow-band red emission peak at 610-630 nm with high color purity; however, the weak and narrow absorption band in the NUV region limits their applications. Doping a higher amount of Eu³⁺ ions into a non-concentration quenching host could be key to enhancing the efficiency of the absorption value and emission intensity. Hence, the design of Eu³⁺-heavily doped phosphors with a suitable host lattice is key for applications. In this study, red-emitting Eu³⁺-doped Gd(BO₂)₃-Y₃BO₆-GdBO₃ (GdYGd:Eu³⁺) phosphor with a high quantum efficiency of 58.4% and excellent color purity of 99.5% is reported for the first time. The phosphor is efficiently excited by NUV light at 394 nm and emits a strong red emission band in the 590-710 nm range, peaking at 612 nm. The optimal annealing temperature and Eu³⁺ doping content to obtain the strongest PL intensity are 1100 °C and 20 mol%, respectively. The optimized GdYGd:Eu³⁺ phosphor possesses a high activation energy of 0.319 eV and a lifetime of 1.14 ms. An illustration of phosphor-coated NUV LED with chromaticity coordinates (x = 0.5636,y = 0.2961) was successfully synthesized, demonstrating the great potential of GdYGd:Eu³⁺ phosphor for NUV-pumped WLED applications.