According to Stokes’ law, materials can only be excited by high energy light and emit low energy light. In other words, materials can emit long wavelength and low frequency light when excited by short wavelength and high frequency light.
On the contrary, upconversion luminescence refers to the material is excited by light with low energy and emits light with high energy. In other words, the material emits light with short wavelength and high frequency when excited by light with long wavelength and low frequency.
Up to now, upconversion luminescence has occurred in compounds doped with rare earth ions, mainly fluoride, oxide, sulfur compounds, fluorine oxides, halides, etc.
NaYF4 is the substrate material with the highest up-conversion luminescence efficiency. For example, when NaYF4: Er, Yb, i.e., ytterbium and erbium are double-doped, Er acts as the activator and Yb as the sensitizer.
Post time: Apr-21-2021