Investigation of reversible photoluminescence switching driven by colorless-purple photochromism in Sr5(PO4)3F:Eu2+ for optical storage applications

We report a novel photoresponsive powder material, haloapatite Sr5(PO4)3F:Eu2+, which exhibits good photochromic properties and undergoes reversible colorless-purple color changes after alternative UV and visible irradiation/heating. The effect of Eu2+ doping concentration on the photochromic behavior is investigated, and the optimum doping concentration of Eu2+ is found to be approximately 0.5 mol%. Further recycling coloring-bleaching measurements at room and high temperature confirm the high fatigue resistance of the material and the good thermal stability of its photochromic performance. Based on these findings, the photoluminescence performance of the present material can be effectively modulated through its photochromism. A luminescence switching efficiency of up to ∼40% is obtained for x = 0.005. The present results allow discussing the critical role of the charge carrier dynamics in the photochromism. Finally, we propose a tentative model illustrating the photochromism and luminescence modulation mechanisms.