Crystal structure characterization, optical and photoluminescent properties of tunable yellow- to orange-emitting Y2(Ca,Sr)F4S2:Ce3+ phosphors for solid-state lighting

Abstract

In this study, a new efficient Ce³⁺-doped fluorosulfide phosphor, Y₂(Ca,Sr)F₄S₂:Ce³⁺, was obtained by using solid-state methods in a sealed silica ampoule. The synthesized Y₂(Ca,Sr)F₄S₂:Ce³⁺ was characterized by powder X-ray diffraction and refined with Rietveld methods. Y₂(Ca,Sr)F₄S₂:Ce³⁺ can be excited by blue light (440–470 nm) and shows yellow-to-orange broadband emission peaking at 553–590 nm with a quantum efficiency of 16–31%. Non-radiative transitions between Ce³⁺ ions in Y₂CaF₄S₂:Ce³⁺ and Y₂SrF₄S₂:Ce³⁺ hosts have also been demonstrated to be attributable to dipole–dipole interactions, and the critical distances were calculated to be 18.9 and 19.3 Å. The possible mechanism of the tunable luminescence properties was described on the basis of band structure calculations. In addition, a white LED device was fabricated by using Y₂(Ca,Sr)F₄S₂:Ce³⁺ phosphor pumped with a 460 nm blue chip. The CRI value and CCT were measured to be 74–85 and 3500–8700 K, respectively, showing promising potential for solid-state lighting.