Effect of Eu^{3 +} codoping on upconversion luminescence in Y₂O₃:Er^{3 +}, Yb^{3 +} nanocrystals

The influence of Eu³⁺ on the upconversion (UC) fluorescence of Er³⁺ in Y ₂O₃:Er³⁺, Y b³⁺ nanocrystals was investigated. Room-temperature UC spectra show that the intensity ratio of red to green lights was increased from 8.6 to 19.3 with 1.0 mol% Eu³⁺ doping. Additionally, with the increase of Eu³⁺ ion concentration, the n values for both green and red UC emissions in Y ₂O₃:Er³⁺, Y b³⁺ nanocrystals become larger. Our analysis shows that the energy transfer between Eu³⁺ and Er³⁺ ions is the main cause for the enhancement of ²H_11/2, ⁴ S_{3 / 2} → ⁴ F_{9 / 2} and ⁴ I_{11 / 2} → ⁴ I_{13 / 2} transitions of Er³⁺ ions.