Effect of Tb³⁺ and Ce³⁺ Co-doping on the Structure and Photoluminescence Properties of Hexagonal Boron Nitride Phosphors

In the paper, we have successfully prepared hexagonal boron nitride (h-BN:Tb³⁺, Ce³⁺) phosphors with melamine as the nitrogen source. The X-ray powder diffraction patterns confirm that the sample possesses a hexagonal crystal structure within the P \(\overline6\) $\overline{6}$ m2 space group. It is interesting that the co-doping combination of Tb³⁺ and Ce³⁺ can markedly enhance the threshold concentration of doped activators within the limited solid solution of h-BN phosphors. Under 302 nm excitation, the h-BN:Ce³⁺ phosphors exhibit broadband blue light emission at 406 nm. In h-BN:Tb³⁺, Ce³⁺ phosphors, the co-doping of Ce³⁺ not only ensures high phase purity but also results in strong green light emission. The energy transfer efficiency from Ce³⁺ to Tb³⁺ is about 55%. The fluorescence lifetime increases with the increase of Ce³⁺ and Tb³⁺ concentration, and the fluorescence lifetime of h-BN:0.025Tb³⁺, 0.05Ce³⁺ phosphor reached 2.087 ms. Additionally, the h-BN:0.025Tb³⁺, 0.05Ce³⁺ phosphor exhibits excellent thermal performance with an activation energy value of 0.2825 eV. Moreover, the photoluminescence quantum yield of the sample exceeds 52%. Therefore, the h-BN:Tb³⁺, Ce³⁺ samples can be used as green phosphors for solid state lighting and fluorescent labeling.