First-principles investigation of electronic structure and energy level scheme of phosphors: The lanthanide-doped Sr₂P₂O₇

Using screened hybrid density functional theory (HSE06), the electronic structure, character of electronic transition and energy level scheme of lanthanide (Ln)-doped Sr₂P₂O₇ are systematically investigated. Both Ln²⁺ and Ln³⁺ dopants are considered. It is found that, owing to the doping of Ln²+/3⁺ ions, some extra Ln 4 f and 5d states are introduced in the host Sr₂P₂O₇ band gap, causing a change in the electronic structures and the luminescence properties. The specific locations of the Ln 4 f and 5d states and the possibility of electronic transitions, especially the 4 f → 5d, are systematically studied. The energy level scheme is constructed from the calculated electronic structures, and it fits well with the experimental scheme. This work gives a whole picture of the Ln doping effect on the materials. It can be applied to all Ln-doped fluorescent materials and to aid in the discovery of new bright scintillator materials.