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 K3Lu(PO4)(2): Tb3+, Eu3+ 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 K3Lu(PO4)(2) were analyzed by the first -principles method. The cross-relaxation of Tb3+-doped phosphors was investigated as well. The ET from Tb3+ to Eu3+ ions, realizing through the electric dipole-dipole (d-d) interaction with a high ET efficiency of 98.36%, could be controlled principally by the Tb3+/Eu3+ 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 BaMgAl10O17: Eu2+ phosphors, green-emitting SiAlON: Eu2+ phosphors, and orange-red-emitting K3Lu(PO4)(2): 0.1 Tb3+, 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.