Highly efficient red upconversion fluorescence emission in Yb3+/Ho3+/Ce3+ codoped LaF3 nanocrystals

The Yb3+/Ho3+/Ce3+ codoped LaF3 nanocrystals have been successfully prepared via a facile hydro-thermal method. The significant enhancement in the red upconversion emission of Ho3+ is successfully obtained in LaF3:Yb3+/Ho3+ nanocrystals through introducing of Ce3+ under NIR excitation at 980 nm. The red-to-green emission ratio of Ho3+ is enhanced 18.9-fold with Ce3+ concentration increasing to 12%, which is due to the two efficient cross relaxation processes of I-5(6) (Ho3+)+F-2(5/2) (Ce3+)-> I-5(7) (Ho3+)+P-2(7/2) (Ce3+) and S-5(2)/E-5(4) (Ho3+)+F-2(5/2) (Ce3+)-> F-5(5) (Ho3+)+F-2(7/2) (Ce3+) between Ho3+ and Ce3+ ions. The enhancement mechanism of red emission and conversion efficiency between Ho3+ and Ce3+ are investigated in detail. (C) 2016 Elsevier B.V. All rights reserved.