Luminescence and energy transfer of a color tunable phosphor: Ba2CaLa1−xMx(PO4)3 (M=Dy, Tm, Eu) for warm white UV LEDs

A series of Dy3+-, Tm3+-, Eu3+ co-activated Ba2CaLa(PO4)3 phosphors were synthesized via a standard solid state reaction under normal ambient air, and the emission colors could be tuned from blue to white and then to red. It was discovered that the energy is transferred from Tm3+ to Dy3+ by directly observing overlap of the excitation spectrum of Dy3+ and the emission spectrum of Tm3+ and Dy3+. By utilizing the principle of energy transfer, we have demonstrated that with appropriate tuning of activator content, Ba2CaLa1−x−y−z(PO4)3:xDy3+–yTm3+–zEu3+ phosphors exhibit great potential for use as single-component phosphors for warm white ultraviolet light-emitting diodes (UV LEDs).