Bright white up-conversion emission from Er3+/Ho3+/Tm3+/Yb3+ co-doped YVO4 phosphors

Er3+/Ho3+/Yb3+/Tm3+ co-doped YVO4 phosphors were synthesized by the conventional solid-state reaction. Under 980 nm laser diode excitation, intense red, green and blue up-conversion emissions were observed for the Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ couples in the YVO4 host, respectively, which were due to the successive energy transfer from Yb3+ to Er3+, Ho3+ or Tm3+. Bright white luminescence upon 980 nm near-infrared excitation can be observed for the sample at the optimum chemical composition of YVO4:10%Yb3+/1%Tm3+/0.3%Ho3+/0.2%Er3+. Under different excitation pump powers, the obtained optimal color coordinate (0.323, 0.325) is very close to the standard white light (0.333, 0.333) coordinate.