Tunable luminescence properties and energy transfer of Tm3+, Dy3+, and Eu3+ co-activated InNbO4 phosphors for warm-white-lighting

Abstract

A series of Dy3+/Tm3+ singly-doped, Dy3+/Tm3+ co-doped, and Dy3+/Tm3+/Eu3+ tri-doped InNbO4 phosphors have been synthesized by a high-temperature solid-state reaction method. Powder X-ray diffraction (XRD), structure refinement, UV–visible diffuse reflectance (UV-DR) spectrum, photoluminescence excitation (PLE) and emission (PL) spectrum, decay lifetimes and CIE chromaticity coordinate were employed to understand the origins of luminescence properties for synthesized phosphors. Rare-earth activators were determined to be completely dissolved into the host lattice and occupied the 2e sites deviated from an inversion center by virtue of XRD, structure refinement and photoluminescence features. The photoluminescence excitation spectra of phosphors exhibited a broad excitation band ascribed to charge-transfer of O2−-Nb5+, ranging from 200 to 300nm, and some characteristic excitation peaks associated with energy level transition of RE ions. Under the excitation of UV light, phosphors presented characteristic emission originating from f-f transition within the 4f configuration of RE ions. With increasing Dy3+ concentration, emission colors of InNbO4:Tm3+, Dy3+ phosphors can be appropriately tuned from blue to yellow, including almost all the white light region, by means of energy transfer from Tm3+ to Dy3+. Energy transfer rates and efficiencies were calculated according to decay lifetimes and energy transfer mechanism followed a resonant type dipole-dipole interaction with critical distance of 22.23Å between Tm3+ and Dy3+. By compensating a red component of Eu3+ ion, single-component warm-white-light emitting was realized in InNbO4:Tm3+,Dy3+,Eu3+ phosphors. They might be promising candidates for color-tunable light-conversion components in the fabrication of ultraviolet-pumped warm-white-light emitting diodes (WLEDs) for solid-state lighting. Relationship of crystal structures and luminescence properties for InNbO4 and YNbO4 phosphors is as well explicated based on structural analysis.