Enhancing External Quantum Efficiency of Blue-Emitting Phosphor Ba(K)-β-Al<sub>2</sub>O<sub>3</sub>:Eu<sup>2+</sup> by Lattice Site Engineering for Full-Spectrum Lighting
Chao Dou, Shengqiang Liu, Fangyi Zhao, Zhen Song, Quanlin Liu
Abstract
The discovery of violet-excitable blue-emitting phosphor is a significant breakthrough for the development of phosphor-converted full-spectrum white light-emitting diodes (WLEDs). However, the application of most known violet-excitable blue-emitting phosphors is limited by their low external quantum efficiency (EQE). In this work, we reported on how the EQE values of Eu 2+ -doped Ba(K)-β-Al 2 O 3 blue-emitting phosphor can be significantly improved through lattice site engineering. By partially substituting K + for Ba 2+, the Eu 2+ -occupied crystallographic site changes and the coordination polyhedron of Eu 2+ shrinks, leading to the increase of crystal field splitting. Consequently, the excitation spectrum exhibits a continuous red shift to match the violet excitation, which enhances the PL intensity of solid solution phosphor (Ba 0.4 K 1.6 ) 0.84 Al 22 O 35−α:0.32Eu 2+ ((B 0.4 K 1.6 ) 0.84 AO:Eu) by 1.42 times compared to that of the end-member Ba 1.68 Al 22 O 35−α:0.32Eu 2+ (B 1.68 AO:Eu) phosphor. Correspondingly, under the 400 nm violet light excitation, the EQE of optimal blue-emitting (B 0.4 K 1.6 ) 0.84 AO:Eu phosphor is up to 53%. Additionally, the phosphor also shows excellent resistance to luminescence thermal quenching (95% at 150 °C). Finally, the WLED fabricated based on (B 0.4 K 1.6 ) 0.84 AO:Eu and commercial green and red phosphors exhibited an ultra-high color rending index with Ra = 95.5 and R1–R15 >90. This work offers guidance for tuning the spectral properties of phosphors through lattice site engineering.