Upconversion Emission Enhancement in Yb3+/Er3+-Codoped Y2O3 Nanocrystals by Tridoping with Li+ Ions

Abstract

We demonstrate that tridoping with Li + ions enhances the visible green and red upconversion (UC) emissions in Er 3+ /Yb 3+ -codoped Y 2 O 3 nanocrystals by up to half of the bulk counterpart, i.e., about 2 orders of magnitude higher than previous results. X-ray diffraction and decay time investigations give evidence that tridoping with Li + ions can tailor the local crystal field of the Y 2 O 3 host lattice. Theoretical calculations illustrate well that a significant UC intensity enhancement arises from the synthesized tailoring effect induced by the Li + ions, which increase lifetimes in the intermediate 4 I 11/2 (Er) and 2 F 5/2 (Yb) states, increase optically active sites in the Y 2 O 3 host lattice, and dissociate the Yb 3+ and Er 3+ ion clusters in the nanocrytals. The general theoretical description of the visible UC radiations shows that the Yb 3+ ion sensitization and the tailoring effect induced by the Li + ions are two independent enhancement mechanisms, which is expected to lead to an increasing number of photonic and biomedical applications in the future.