Tuning emission color and improving the warm-white persistent luminescence of phosphor BaLuAlGaSiO:Pr Zn co-doping.

In this article, we synthesized a series of new warm-white emitting persistent luminescent phosphors by co-doping Zn into Pr activated BaLuAlGaSiO, and systematically investigated the effect of Zn 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 P and D multiplet electron transitions at the 4f level of Pr. The luminescence properties of the BaZnLuAlGaSiO:Pr phosphors can be modified by changing the content of Ba/Zn in the host, which affects the non-radiative energy flow between 5d-P-D levels and resultantly enhances the intensity of the 4f → 4f transition. Compared with the undoped sample, Zn 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, Zn 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 Zn concentration. Besides, the Zn 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 BaLuAlGaSiO:Pr,Zn phosphor.