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

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-xV2-O-7:Eu-x 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 518 nm, which would be from VO4 groups with approximate C-3v symmetry, and a sharp characteristic spectrum (D-5(0) -> F-7(2)) at about 611 nm 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 x 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 C-3v 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. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.