Comprehension of defect states induced by fluorine ions substituting for oxygen ions in Sr3MgSi2O8−δF2δ by first principles calculation

Abstract

Study of the defect states in the luminescent host materials has always been a significant point in improving the light emitting devices performances. To afford candidate luminescence host materials, defect states in Sr3MgSi2O[Formula: see text]F[Formula: see text] induced by substitution of fluorine ions (F[Formula: see text] substituting for oxygen ions (O[Formula: see text] have been studied through first principles calculation and the related results are presented in this work. First, chemical formulas have been confirmed to be Sr3MgSi2O[Formula: see text]F[Formula: see text] through calculations of the possible crystal structures with increasing F[Formula: see text] substituting for O[Formula: see text] concentrations while band gap values decrease from 5.889 eV to 5.328 eV. When the fluorine ion substituting concentration [Formula: see text] reached 0.5, a new defect state near 3.002 eV in the band gap appeared and it can be concluded that the defect state originates from the two fluorine ions bonding to the same Si–O–F2 group. In addition, there arose a new absorption band in the visible region and it can also be attributed to the introduced color [Formula: see text] center in Sr3MgSi2O[Formula: see text]F. The aforementioned results show that tiny doping amounts of fluorine ions could make Sr3MgSi2O[Formula: see text]F[Formula: see text] suitable for luminescence host materials.