Enhancement of green emission from Tb3+:GdOBr phosphors with Ce3+ ion co-doping

A strong green emission (5D4→7F5) has been observed from Tb3+ (1.0 mol%) doped into GdOBr powder phosphors upon excitation with an UV-wavelength (226 nm). To this phosphor, different amounts of Ce3+ (from 0.1 to 1.5 mol%) have been added to further improve the green emission efficiency of Tb3+-doped GdOBr. It has been found that the optimum concentration, 0.2 mol% of Ce3+, results in a twofold enhancement of the green emission intensity. The green emission from Tb3+ could not be increased at higher Ce3+ concentrations due to the Ce3+-Ce3+ ion interactions, i.e., the concentration quenching effect. The mechanism involved in the energy transfer between the Ce3+ and Tb3+ has been explained with an energy level diagram.