Near-infrared quantum cutting in Ho3+/Yb3+ co-doped BaZr0.8Y0.2O3-δ

A novel HO3+ -> Yb3+ -> Ho3+ multi-step energy transfer caused quantum cutting under 455 nm excitation is observed in Ho3+/Yb3+ co-doped BaZr0.8Y0.2O3-delta phosphor. During the quantum cutting process, Yb3+ ions efficiently increase the particle population of I-5(6) level of Ho3+, resulting in 10 and 8 times of enhancement of HO3+ emission at 1216 nm (I-5(6) -> I-5(8)) and 1926 nm (I-5(7) -> I-5(8)), respectively. It is interesting that the F-2(5/2) -> F-2(7/2) emission of Yb3+ ions themselves is very weak although the quantum cutting is performed by the Ho3+/Yb3+ ion-pairs. The result indicates that the Yb3+ -> Ho3+ back energy transfer in the BaZr0.8Y0.2O3-delta phosphor is quite efficient and helpful for the enhancement of Ho3+ emission in near infrared region. A new valid method based on luminescence intensity ratio is developed to estimate the quantum cutting efficiency. It is found that the energy transfer form Ho3+ to Yb3+ is 52.8% in the phosphor with optimum Ho3+/Yb3+ doping concentration and 90% of near infrared emission of Ho3+ is performed by the multi-step energy transfer induced quantum cutting. (C) 2016 Elsevier B.V. All rights reserved.