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