Theoretical method to select appropriate codopants as efficient foreign electron traps for Lu_3Al_2Ga_3O_12:Tb^3+/Ln^3+ persistent phosphor

Abstract

Spectroscopic data in our investigation, combined with those in references, are used to construct an energy diagram of the typical Lu3Al2Ga3O12:Ln(2+)/Ln(3+) phosphors. Based on the diagram, the persistent luminescence properties of Lu3Al2Ga3O12:Ln(2+)/Ln(3+) (Ln = La-Yb) phosphors are theoretically predicted. We have shown that the position of the 4f ground level of Ln(2+) in the band gap can estimate the ability of Ln(3+) codopants as foreign electron traps, and it is confirmed by our experimental results of the typical Lu3Al2Ga3O12:Tb3+, Ln(3+) samples. Finally, the critical roles of the Yb3+ codopants as efficient foreign traps in the typical Lu3Al2Ga3O12:Tb3+ phosphor is revealed. The requirements for efficient foreign traps and the fundamental persistent luminescence mechanism of this phosphor are systematically summarized. (C) 2016 Optical Society of America