Efficient oxide phosphors for light upconversion; green emission from Yb3+ and Ho3+ co-doped Ln(2)BaZnO(5) (Ln = Y, Gd)

The optical properties of Yb3+ and Ho3+ co-doped Y2BaZnO5, synthesized by solid-state reactions, are investigated in detail. Under 977 nm excitation (similar to 25 x 10(-3) W mm(-2)), bright green upconversion emission is observed. Concentration dependence studies at room temperature show that relatively high infrared to visible upconversion efficiencies are obtained with values up to similar to 2.6%. The results of power dependence studies and temperature-dependent lifetime measurements allow us to determine the dominant upconversion mechanisms in Yb3+: Ho3+ co-doped Y2BaZnO5 oxides. The materials presented in this article constitute new and efficient upconversion phosphors which may find utility in a variety of applications.