Band structure, photoluminescent properties, and energy transfer behavior of a multicolor tunable phosphor K3Lu(PO4)2: Tb3+, Eu3+ for warm white light-emitting diodes

A series of original tunable-luminescence phosphors K 3 Lu(PO 4 ) 2 : Tb 3+ , Eu 3+ with efficient energy transfer (ET) was synthesized using a high-temperature solid-state reaction. The samples were characterized via X-ray powder diffraction, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, CIE chromaticity coordinates, and fluorescence decay analysis. The energy band and density of states of K 3 Lu(PO 4 ) 2 were analyzed by the first-principles method. The cross-relaxation of Tb 3+ -doped phosphors was investigated as well. The ET from Tb 3+ to Eu 3+ ions, realizing through the electric dipole-dipole (d-d) interaction with a high ET efficiency of 98.36%, could be controlled principally by the Tb 3+ /Eu 3+ doping concentration ratio, yielding the tunable emissions from green (0.293, 0.537) to orange-red (0.563, 0.367) range. Based on the obtained results, a three-phosphor-conversion white light-emitting diode (w-LED) was fabricated through the integration of a 365 nm chip and commercial blue-emitting BaMgAl 10 O 17 : Eu 2+ phosphors, green-emitting SiAlON: Eu 2+ phosphors, and orange-red-emitting K 3 Lu(PO 4 ) 2 : 0.1 Tb 3+ , 0.06Eu 3+ phosphors. The appliance emits the white light at a suitable correlated color temperature of 3678 K and a high color rendering index of 91.4. These parameters are almost equal to those of ideal white light, which opens up the prospects for using this up-and-coming phosphor for warm w-LED applications.