Yellow upconversion luminescence in Ho3+/Yb3+ co-doped Gd2Mo3O9 phosphor

The strong yellow upconversion (UC) light emission was observed in Ho3+/Yb3+ co-doped Gd2Mo3O9 phosphor under the excitation of 980 nm diode laser. The phosphors were synthesized by the traditional solid-state reaction method. The structures of the samples were characterized by X-ray diffraction (XRD). Under 980 nm excitation, Ho3+/Yb3+ co-doped Gd2Mo3O9 exhibited strong yellow UC emission based on the green emission near 541 nm generated by 5F4,5S2 → 5I8 transition and the strong red emission around 660 nm generated by 5F5 → 5I8 transition, which assigned to the intra-4f transitions of Ho3+ ions. The doping concentrations of Ho3+ and Yb3+ were determined to be 0.01 mol Ho3+ and 0.2 mol Yb3+ for the strongest yellow emission. Then the dependence of UC emission intensity on excitation power density showed that the green and red UC emissions were involved in two-photon process. The possible UC mechanisms for the strong yellow emission were also investigated. The result indicated that this material was a promising candidate for the application in the yellow display field.