Trap distribution and photo-stimulated luminescence in LaSrAl3O7:Eu2+ long-lasting phosphors for optical data storage

Here, a green emission persistent luminescent phosphor LaSrAl₃O₇:Eu²⁺ which is chargeable by UV light, was synthesized by solid-state reaction method. Elemental mapping and fluorescence microscopy photoluminescence of the sample demonstrated the homogeneous distribution of La, Sr, Al, O, and Eu in the phosphor. Rietveld refinement shows that the as-prepared sample belongs to the tetragonal crystalline structure with space group of P42₁m. The Eu²⁺:5d-4f broad persistent luminescence with maximum emission peaking at 518 nm can be effectively obtained after irradiating in the UV light. A series of excitation temperature-dependent thermoluminescence measurements were conducted to gain some insight into the information of traps. Additionally, to verify its feasibility of optical data storage, specific information letters were encoded on the LaSrAl₃O₇:Eu²⁺ phosphor films using the laser of 405 nm, then the stored information could indeed be read out by thermal stimulation as expected. Meanwhile, NIR photo-stimulated red persistent luminescence was also obtained, which holds great potential for optical information storage. Finally, combined with the experimental and density functional theory calculation results, we proposed a tentative schematic diagram to account for the PersL and photo-stimulated persistent luminescence mechanism in LaSrAl₃O₇:Eu²⁺ phosphor.