Adjustable ultraviolet and white light dual emission phosphor Y2Sr(Ga1-yAly)4SiO12:xPr3+ for health lighting

Mid-ultraviolet light (290-320 nm) can promote human vitamin D synthesis, which helps in the prevention and treatment of rickets and cartilage disease. For people who lack sufficient ultraviolet radiation all year round, it is significant to supplement the ultraviolet component in daily lighting sources. However, there are few luminous materials showing a combination of mid-ultraviolet light and white light emission on the market. Here, we designed a new material, Y2Sr(Ga1-yAly)4SiO12:xPr3+ (YSGAS:xPr3+), which achieves dual emission of 320 nm ultraviolet and white light from a single substrate with a single doped phosphor. Without Al3+ ions, the emission intensity of the Y2SrGa4SiO12:xPr3+ phosphor shows a contribution-dependent relationship, and concentration quenching due to exchange interaction. The crystal field environment was regulated by partially replacing Ga3+ ions with Al3+ ions. After introducing Al3+, YSGAS:xPr3+ phosphors exhibit dual ultraviolet emission (320 nm) and visible light emission. The emission color of YSGAS:xPr3+ can be adjusted by changing the Al3+ concentration, and Y2Sr(Ga0.6Al0.4)4SiO12:1%Pr3+ emits both ultraviolet light and white light. The LED device prepared by using the YSGAS:Pr3+ phosphor and chips shows a color temperature of 4858 K and appropriate CIE coordinates of (0.3474, 0.3390), indicating wide application prospects in the field of "health lighting" for particular populations.

Tuning emission color and improving the warm-white persistent luminescence of phosphor BaLu2Al2Ga2SiO12:Pr3+via Zn2+ co-doping

In this article, we synthesized a series of new warm-white emitting persistent luminescent phosphors by co-doping Zn²⁺ into Pr³⁺ activated BaLu₂Al₂Ga₂SiO₁₂, and systematically investigated the effect of Zn²⁺ co-doping on both their photoluminescence and persistent luminescence properties. Following the removal of UV excitation, the phosphor emits warm-white persistent luminescence consisting of greenish-blue and red emissions originating from ³P₀ and ¹D₂ multiplet electron transitions at the 4f level of Pr³⁺. The luminescence properties of the Ba_1-xZn_xLu₂Al₂Ga₂SiO₁₂:Pr³⁺ phosphors can be modified by changing the content of Ba/Zn in the host, which affects the non-radiative energy flow between 5d¹-³P₀-¹D₂ levels and resultantly enhances the intensity of the 4f → 4f transition. Compared with the undoped sample, Zn²⁺ co-doping can significantly enhance the persistent luminescence intensity of the phosphors in the range of 400-800 nm and reduce the intensity in the UV region. Meanwhile, Zn²⁺ co-doping can also change the intensity ratio between the greenish-blue and red emissions, and the persistent luminescence color can be tuned from red to warm-white with the increase of Zn²⁺ concentration. Besides, the Zn²⁺ ions entering the crystal lattice also enhance the persistent luminescence performance by modifying the defect levels in the phosphor. For the optimized phosphor, bright warm-white persistent luminescence can be observed by the naked eye in the dark after the removal of the excitation source for 4 h. Based on the experimental results, a feasible mechanism was also proposed to reveal the persistent luminescence generation process for the BaLu₂Al₂Ga₂SiO₁₂:Pr³⁺,Zn²⁺ phosphor.

Long persistent phosphors—from fundamentals to applications

We present multidisciplinary research on synthetic methods, afterglow mechanisms, characterization techniques, material kinds, and applications of long persistent phosphors.