Chuanlong Wang

Trap distribution tailoring guided design of super-long-persistent phosphor Ba2SiO4:Eu2+,Ho3+ and photostimulable luminescence for optical information storage

Here, we report a novel long-persistent luminescence (LPL) phosphor, Ba2SiO4:Eu2+,Ho3+. The crystal structure, photoluminescence, photoluminescence excitation and LPL decay behaviors were studied systematically. The developed LPL phosphor Ba2SiO4:Eu2+,Ho3+ shows super-LPL, which remains above 2.97 mcd m−2 even 24 h after the removal of UV irradiation source. The outstanding LPL performance is mainly derived from the tailoring of trap distribution via Ho3+ co-doping. 15 days after UV irradiation, the sample still shows observable green luminescence by 980 nm stimulation. By means of photostimulated luminescence (PSL), excitation duration, decay duration and excitation temperature dependent thermoluminescence spectra, the continuous trap distribution, trap distribution modulation and dynamics of electron motion are characterized. The role of co-dopant Ho3+ serving as electron traps and the tailoring of trap distribution are revealed. The fabrication of Ba2SiO4:Eu2+,Ho3+ phosphor film allows optical information write-in after passing UV light through a photomask (projection printing method) and then the stored information is read out by thermal stimulation or 980 nm photostimulation, which holds great promise for optical information storage. Moreover, combined with the experimental and DFT calculation results, a tentative schematic diagram is proposed for the illustration of LPL and PSL mechanism in Ba2SiO4:Eu2+,Ho3+.

Sr3YLi(PO4)3F:Eu2+,Ln3+: colorless-magenta photochromism and coloration degree regulation through Ln3+ co-doping

Herein, novel photochromic materials, Sr3YLi(PO4)3F:Eu2+,Ln3+, have been prepared by a conventional high-temperature solid-state reaction. Eu2+ singly doped Sr3YLi(PO4)3F showed reversible colorless-magenta photochromism when alternately irradiated by UV and visible light (or thermal treatment). Thus, Sr3YLi(PO4)3F:Eu2+ might be a potential candidate in various fields such as in imaging, sensors, photo-switches, and erasable optical storage media. The optimal Eu2+ doping concentration is experimentally determined to be about 0.5 mol%. The coloring and bleaching processes are attributed to electron trapping accompanied by the generation of F-centers and detrapping by different traps, respectively. Thus, these processes open a window for us to design a simple way to regulate and control the photochromic performance just by adjusting the doping concentration of Eu2+ ions or co-doping Ln3+ ions. On the basis of thermoluminescence, a schematic of a photochromic mechanism has also been proposed.