Effect of Mn substitution on electronic structure of Ca9Y(PO4)7:Eu2+, Mn2+ phosphor determined by X-ray absorption spectroscopy

► The first XAS and photoluminescence report on Ca9Y(PO4)7:Eu2+, Mn2+ phosphors. ► The PL demonstrated the energy transfer between Eu and Mn. ► The energy transfer is ascribed to charge transfer between Eu-Mn revealed by XAS. ► The PL intensity depends on the formation of Mn-related state in the conduction band. ► The band gap narrowing is due to the formation of Mn-related state.