How to tune trap properties of persistent phosphor: Photostimulated persistent luminescence of NaLuGeO4:Bi3+,Cr3+ tailored by trap engineering

We take the NaLuGeO4:Bi3+,Cr3+ as a typical example to show an effective approach to tune the trap properties of persistent phosphor as needed. An empirical law concerning the trap engineering is summarized based on the experimental results and a large number of references. Guided by this law, the trap properties of this material are effectively tailored by Cr3+ codopants, and consequently the degradation of the infrared-to-ultraviolet persistent luminescence is greatly reduced. The calculations and a serial of thermoluminescence experiments have been conducted to verify the effect of the trap engineering. The infrared-to-ultraviolet persistent luminescence and trap properties are investigated in details. It demonstrates that the proposed empirical law concerning the trap engineering is indeed valid and the NaLuGeO4:Bi3+,Cr3+ material is potential for photodynamic therapy.