Multiband Monte Carlo modeling of upconversion emission in sub 10 nm β-NaGdF4:Yb3+, Er3+ nanocrystals—Effect of Yb3+ content

Abstract

In this work, we report the results of theoretical modeling supported and confirmed by experimentally measured emission, emission decay curves, and power dependent emission spectra for sub 10 nm β-NaGdF₄:Er³⁺,Yb³⁺ nanocrystals with different Yb³⁺ content (0.5%-15%). For the theoretical analysis, we develop a stochastic Monte Carlo model which is based on two components: (i) formation of clusters composed of Er³⁺ ion and Yb³⁺ neighbors, which gives insight into the role of local parameters and (ii) a simplified kinetic model of excitation and relaxation phenomena in pairs of Er³⁺and Yb³⁺ ions. The quantitative agreement between experimental data and modeling was obtained for the relative emission ratio of upconversion luminescence in green, red, and blue spectral ranges. Theoretical predictions of impact of excitation pulse duration and pumping light power on upconversion luminescence are presented.