Dual-luminescence-center single-component white-light Sr2V2O7:Eu3+ phosphors for white LEDs

Abstract

Single-component white-light phosphors can overcome many of the problems associated with multiple emitting components, such as intrinsic color balance, device complications and high cost. Here, we demonstrate a novel type of single-component white-light Sr2−xV2O7:Eux phosphor with dual-luminescence centers (x=0–0.24) for white light-emitting diodes (LEDs). Due to the charge transfer absorption (V5+O42-→V4+O42-), the white light spectra they emit consist of both a broad photoluminescence band centered at about 518nm, which would be from VO4 groups with approximate C3v symmetry, and a sharp characteristic spectrum (5D0→7F2) at about 611nm from the doped Eu3+ ion at the Sr2+ sites in the Sr2V2O7 crystal. Moreover, to explain the broad emission spectra of these phosphors, a 10×10 energy matrix was successfully established based on an effective operator Hamiltonian, including free ion and crystal field interactions. For the first time, the broad emission spectra for VO4 groups with the approximate C3v symmetry were calculated using a complete diagonalization (of energy matrix) method. The fitting and experimental values are close to each other, powerfully demonstrating the nature of this broad emission and the feasibility of using the complete diagonalization method to study the phosphors for white LEDs.