White upconverted luminescence of Ho3+/Yb3+/Tm3+ tri-doped Gd2Mo3O9 phosphors

Yb3+/Tm3+/Ho3+ tri-doped Gd2Mo3O9 phosphors were synthesized by the high-temperature solid-state method. Under 980 nm near-infrared excitation, the white-light emission can be observed, which is consists of the blue, green, and red UC emissions. The green and red emission at 547 nm and 660 nm originated from the transition of Ho3+ (5S2, 5F4 → 5I8 and 5F5 → 5I8) and the blue emission at 475 nm attributed to the transition of Tm3+ (5G4 → 5H6). In this experiment, we selected the optimum concentration ratio of the three rare earths for the bright white emission. The Commission internationale de L’Eclairage (CIE) coordinates for the samples were calculated, and chromaticity coordinates were very close to white light regions. We find that the calculated CIE color coordinates of the Yb3+/Tm3+/Ho3+ tri-doped Gd2Mo3O9 phosphors changed with the incident pump power from 400 mW/cm2 to 1000 mW/cm2. The upconversion luminescence mechanism of the samples was discussed on its spectral. The white light may be proved to be a candidate material for applications in various fields.