High yield multispectral upconversion emission in Y2Te4O11:Er:Yb nanocrystals on green and NIR excitations

Abstract

Detailed synthesis, structural, thermal and radiative properties of Er and Er:Yb codoped Y₂Te₄O₁₁ nanocrystals were discussed. Nanocrystals were synthesized by a solid state method and reported to emit bright emissions in the wide range of blue-IR regions on excitation with 266 nm, 532 nm and 808 nm laser radiations via one and two photon absorption processes. We have reported a rarely observed ∼711 nm peak at 266 and 532 nm excitations. The emission intensity increases to a great extent in annealed samples and is explained on the basis of crystal structure. Judd–Ofelt theory has been employed to estimate several radiative parameters and the effect of structural modifications due to annealing. Emission intensity was found to reduce in the presence of Yb³⁺ ions which is suggested due to backward energy transfer from Er → Yb ions. Power dependence and time resolved spectroscopic techniques were used to explore excitation and emission dynamics. These studies clearly indicate promising and futuristic applications of such material for optical fibers and luminescent devices.