The photoluminescence properties of Eu,Bi co-doped yttrium oxysulfide phosphor under vacuum ultraviolet excitation

Y₂O₂S co-doped with Bi³⁺,Eu³⁺ phosphors were prepared and their luminescence properties under vacuum ultraviolet (VUV) excitation were investigated. Much stronger red emission for Y₂O₂S:Eu³⁺,Bi³⁺ were observed under 147 nm excitation than that for Y₂O₂S:Eu³⁺. Investigation on photoluminescence and calculation of electronic structure of Y₂O₂S:Eu³⁺,Bi³⁺ revealed that the Bi³⁺ acts as a medium in energy transfer process and the great VUV luminescence enhancement of Y₂O₂S:Eu³⁺ by doping Bi³⁺ is due to effective energy transfer process: charge transfer (CT) transition of Y³⁺-O²⁻ → Bi³⁺ → Eu³⁺. The Y₂O₂S:Eu³⁺,Bi³⁺ showed excellent optical properties when compared with the commercial (Y,Gd)BO₃:Eu³⁺. Thus, the Y₂O₂S:Eu³⁺,Bi³⁺ would be a promising VUV-excited red phosphor.