High luminescent TiO2-Yb2O3: Er, Li complex nano spherical upconversion phosphor prepared by a hydrothermally treatment

Green upconversion (UC) luminescent spherical TiO₂-Yb₂O₃: Er, Li complex nanocrystals (about 62 nm) were hydrothermally prepared at 120 °C for 6 h then annealed at 800 °C for 4 h. The prepared TiO₂-Yb₂O₃: Er, Li complex nanocrystal are anatase titanium dioxide and cubic ytterbium oxide complex structure. We compared the UC luminescence of samples with the Er concentration when fixed the Yb and Li at 10% and 20%, respectively. All samples showed UC emission peaks near 560, 660 and 845 nm. When the doping concentration of Er was 1.5%, the strongest green UC emission was achieved. The bright green light is observed by the naked eye under lighting conditions. Doping the appropriate proportion of Er,Yb and Li, using suitable process to form a complex to reduce phonon energy also obtained strong UC luminescent nanoparticles. The effective way is extended the effective energy transfer from Yb³⁺ to Er³⁺ as well as reduced the non-radiative decay. The UC luminescence mechanism was discussed.