Intense red upconversion fluorescence emission in NIR-excited erbium-ytterbium doped laponite-derived phosphor

In this report the optical properties and energy-transfer frequency upconversion luminescence of Er³⁺/Yb³⁺-codoped laponite-derived powders under 975 nm infrared excitation is investigated. The 75%(laponite):25%(PbF₂) samples doped with erbium and ytterbium ions, generated high intensity red emission around 660 nm and lower intensity green emission around 525, and 545 nm. The observed emission signals were examined as a function of the excitation power and annealing temperature. The results indicate that energy-transfer, and excited-state absorption are the major upconversion excitation mechanism for the erbium excited-state red emitting level. The precursor glass samples were also heat treated at annealing temperatures of 300 °C, 400 °C, 500 °C, and 600 °C, for a 2 h period. The dependence of the visible upconversion luminescence emission upon the annealing temperature indicated the existence of an optimum temperature which leads to the generation of the most intense and spectrally pure red emission signal.