Enhancement of the upconversion photoluminescence intensity in Li+ and Er3+ codoped Y2O3 nanocrystals

Infrared-to-visible upconversion luminescence spectra are investigated in Li+ and Er3+ codoped Y2O3 nanocrystals. By introducing Li+ ions, the upconverted emission intensity is found to be greatly enhanced when compared with the nanocrystals with the Li+ absent. The cause of the enhancement is believed to be the modification of the local symmetry of the Er3+ ion, which increases the intra-4f transitions of Er3+ ion, and the homogeneous distribution of Er3+. While in some other Er3+ doped oxides, such as ZnO, ZrO2, etc., the upconversion intensity of Er3+ ions could also be greatly increased by doping Li+. (c) 2008 Elsevier B.V. All rights reserved.