Tunable luminescence and energy transfer properties in YPO4:Tb3+, Eu3+/Tb3+ phosphors

Green emitting YPO4:Tb3+ and orange-red emitting YPO4:Tb3+, Eu3+ phosphors were prepared by conventional solid-state reaction and characterized in order to develop materials for applications in white light-emitting diodes (w-LED). First, the doping level of singly doped YPO4:Tb3+ was systematically increased in order to obtain the highest green-to-blue emission intensity ratio through the quenching of the 5D3 emission, by maintaining an acceptable degree of total luminescence. The best emission performance, in terms of color purity and intensity, was obtained with a 5 mol% concentration. Starting from this result, we have synthesized and measured the emission properties of the co-doped phosphors and investigated the Tb3+ to Eu3+ energy transfer (ET) mechanism. The possibility of tuning the color of the luminescence by properly adjusting Eu3+ concentration was finally discussed.