Effect of Yb3+ and Tm3+ concentrations on blue and NIR upconversion luminescence in Yb3+, Tm3+ co-doped CaMoO4

Polycrystalline Tm3+/Yb3+ co-doped CaMoO4 UC phosphors were successfully synthesized by a complex citrate-gel method and their upconversion (UC) luminescence was investigated. Under excitation at 980 nm, Tm3+/Yb3+ co-doped CaMoO4 showed bright blue emission near 475 nm generated by the 1G4→3H6 transition and strong NIR UC emission around 796 nm generated by the 3H4→3H6 transition, with weak red emission near 650 nm due to the 3F2→3H6 transition. The optimum doping concentrations of Tm3+ and Yb3+ for the highest UC luminescence were investigated, and the related UC mechanism of Tm3+/Yb3+ co-doped CaMoO4 depending on pump power was studied in detail.