Tunable warm white emission in Eu3+/Dy3+ co-doped K2Y(WO4)(PO4) phosphors for solid-state lighting

A series of K₂Y(WO₄)(PO₄): Dy³⁺, Eu³⁺ phosphors have been successfully developed via solid-state reaction method to generate color-tunable warm white light. Based on the phase identification and microstructure analysis, Dy³⁺ ions singly-doped and co-doped phosphors all exhibit single phase of K₂Y(WO₄)(PO₄) crystal, demonstrating the substitution of Y³⁺ ions by Dy³⁺ ions in host lattice. Under near ultraviolet (NUV) excitation of 350 nm, Dy³⁺ singly-doped K₂Y(WO₄)(PO₄) phosphors emit a cold-white light with correlated color temperature of 9266 K comprised by blue emission peak at 486 nm and yellow emission peak at 578 nm, which are attributed to ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 electronic transitions of Dy³⁺ ions, respectively. Further, Eu³⁺ and Dy³⁺ ions are co-doped K₂Y(WO₄)(PO₄) host and Eu³⁺ ions can be acted as red emission centers to achieve tunable photoluminescence properties in a single-phased phosphor excited by NUV chip with wavelength of 394 nm. It is proved by the photoluminescence spectra of Eu³⁺ and Dy³⁺ ions co-doped samples that there exist the energy transfer between Dy³⁺ ions and Eu³⁺ ions in the KYWP host, which belongs to the electric dipole-electric dipole interaction. Finally, CIE color coordinates of the generating white light by K₂Y(WO₄)(PO₄): Dy³⁺, Eu³⁺ phosphors can be facilely adjusted from (0.3601, 0.3427) to (0.5161, 0.3547) with the increasing Eu³⁺ ions concentration. The warm white light with tunable color temperatures of 4409 K, 3042 K, 2566 K and 1976 K can be achieved for K₂Y(WO₄)(PO₄): Dy³⁺, Eu³⁺ phosphors, indicating a potential application in NUV white light emitting diodes.