Upconversion mechanisms of Er3+:NaYF4 and thermal effects induced by incident photon on the green luminescence

Wide range concentrations of Er3+ doped NaYF4 nanocrystals are synthesized. Upconversion mechanisms are discussed under 976 nm NIR laser excitation on the basis of the fluorescence spectra and lifetimes data of Er3+. It is found that the heat induced by incident laser results in an evident increase of the slope of emission from 2H11/2 energy level in the pump power dependence. Emission color of samples is investigated and stable chromaticity under different pump power from low and heavy doping samples are found. In addition, upconversion mechanisms are also investigated under 966 nm excitation.