Multiband Monte Carlo modeling of upconversion emission in sub 10 nm β-NaGdF:Yb, Er nanocrystals-Effect of Yb content.

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-NaGdF:Er,Yb nanocrystals with different Yb 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 Er ion and Yb neighbors, which gives insight into the role of local parameters and (ii) a simplified kinetic model of excitation and relaxation phenomena in pairs of Erand Yb ions.