A novel borate phosphor Lu₅Ba₆B₉O₂₇:Ce³⁺ codoped with Sr²⁺/Tb³⁺ for NUV-white light emitting diode application

At present, there are still challenges in developing highly efficient and thermally stable phosphors for ultraviolet/near ultraviolet-white light emitting diodes (UV/NUV-WLEDs). Herein, we use traditional high-temperature solid-state reactions to prepare blue-emitting phosphors Lu_5-Ba₆B₉O₂₇:xCe³⁺ (0.1% ≤ x ≤ 3.0%) and Lu_4.975Ba_6-SrB₉O₂₇:0.5%Ce³⁺ (0% ≤ y ≤ 20%), and green-emitting phosphors Lu_4.975-Ba₆B₉O₂₇:0.5%Ce³⁺,zTb³⁺ (0% ≤ z ≤ 16%), abbreviated as LBB:xCe³⁺, LBB:0.5%Ce³⁺,ySr²⁺ and LBB:0.5%Ce³⁺,zTb³⁺, respectively. Upon 340 nm excitation, LBB:Ce³⁺ exhibits an asymmetric blue emission ranging from 360 nm to 480 nm. Furthermore, the emission intensity of LBB:0.5%Ce³⁺ increased 4.8-fold without a spectral shift through the partial substitution of Sr²⁺ for Ba²⁺. Through constructing the Ce³⁺ → Tb³⁺ energy transfer in the LBB structure, the temperature-dependent integral emission intensity at 483 K improved from only 25% to 68% of the intensity at 303 K due to the existence of fast energy transfer from Ce³⁺ to Tb³⁺. The related results indicate that LBB:xCe³⁺, LBB:0.5%Ce³⁺,ySr²⁺ and LBB:0.5%Ce³⁺,zTb³⁺ phosphors can be used for UV/NUV-WLEDs.