Positive effect of codoping Yb3+ on the super-long persistent luminescence of Cr3+-doped zinc aluminum germanate.

A series of novel near-infrared (NIR) long persistent phosphors of Zn 1.2 Al 1.6 Ge 0.2 O 4 : Cr 3+ , Yb 3+ was synthesized by a solid state method. The crystal structure of Zn 1.2 Al 1.6 Ge 0.2 O 4 was identified. Yb 3+ ions were effective codopants for improving the NIR persistent luminescence intensity even after 100 h of decay. The persistent luminescence decay curves and the thermo-luminescence spectra were analyzed. Results indicated that the increase in efficient electron trap concentration induced by doping Yb 3+ ions was a major factor in the improvement of the NIR persistent luminescence. Moreover, short-wave infrared (SWIR = 900–1700 nm) emission of Yb 3+ was be excited by UV and visible light through charge transfer transition of O 2- –Yb 3+ and energy transfer from Cr 3+ to Yb 3+ , respectively. [ABSTRACT FROM AUTHOR]