Intense Yellow Emission from Gd_0.5-yTb_1.5RE_yW₃O₁₂ (RE=Eu, Sm) Phosphors Tuned through Full Range Doping

Yellow emission phosphors play an important role in fabrication of near ultraviolet (NUV) chip pumped white light emitting diodes (W-LEDs). In this study, doping of Gd₂W₃O₁₂ host with Tb³⁺ and Eu³⁺/Sm³⁺ were used for obtaining yellow light emission. The excitation of Gd³⁺ typically is in deep ultraviolet region, but Gd³⁺ in Gd₂W₃O₁₂ does not emit under the excitation of 382 nm, thus Gd³⁺ does not interfere with the emission from Tb³⁺ and Eu³⁺/Sm³⁺ for obtaining yellow emission. Due to the similar ionic radii, the doping of Gd³⁺ by Tb³⁺ can be achieved in the full concentration range, and at the optimal concentration of 75mol% Tb³⁺, green emission with reasonably high internal quantum efficiency of 37.6% was obtained. With the optimal doping concentration of Tb³⁺, Eu³⁺/Sm³⁺ was co-doped in the Gd₂W₃O₁₂ host, and bright yellow emission with IQE of 39.6% and 47.8% were obtained. The yellow phosphors of Gd_0.494Tb_1.5Eu_0.006W₃O₁₂ and Gd_0.494Tb_1.5Sm_0.006W₃O₁₂ were used to fabricate W-LED devices with NUV-blue chips. Thus, Gd_0.5-yTb_1.5RE_yW₃O₁₂ (RE=Eu, Sm) phosphors are candidates as the yellow phosphors for fabricating W-LED devices. Additionally, the full-range doping strategy can be used in other systems for obtaining efficient phosphors.