Versatile host-sensitized white light emission in a single-component K3ZnB5O10:Dy3+ phosphor for ultraviolet converted light-emitting diodes

Abstract

A single-phase white-light-emitting phosphor, K3ZnB5O10:Dy3+, has been synthesized by a conventional solid-state reaction method. X-ray diffraction (XRD) analysis was used to determine the monoclinic crystal structure of phosphors. The surface states, B 1s, O 1s, K 2p, Zn 2p, and Dy 3d of the phosphor was quantified by X-ray photoelectron spectroscopy (XPS). Diffuse reflectance spectroscopy (DRS) revealed double absorption edges at 3.27 and 5.46 eV for K3ZnB5O10 matrix. The formation of defect-levels, zinc interstitials (Zni), zinc vacancies (VZn), oxygen antisites (OZn) and oxygen vacancies (VO) in K3ZnB5O10:Dy3+ phosphors were identified by photoluminescent (PL) spectroscopy. The emissions at 405 nm (violet-I), 434 nm (violet-II), and 467 nm (blue) are due to intra-band transitions of (FX→VZn), (Zni→VZn) and (Zni→OZn) of the host, respectively. Similarly, the emission at 517 nm (green) corresponds to the transition from free excitons to the oxygen vacancies in the host (FX→VO). The emissions at 575 and 665 nm are assigned to the f-f transitions of Dy3+ ions within the host matrix. An energy level diagram is proposed to describe the host emission and possible energy transfer from the host to dopant ions in the single-phase phosphor. The phosphor shows good thermal stability with activation energy of 0.52 eV. The combined emissions in the blue, green, yellow, and red regions resulted in white light emission with CIE coordinates of (0.256, 0.258) on the CIE diagram.