Synthesis and optical properties of Eu³⁺, Li⁺-codoped ZnO:Zn phosphors

Eu³⁺-Li⁺-codoped ZnO:Zn phosphor with intense sharp line emissions from Eu³⁺ 4f intra-configurational transitions and broad green emission band from defect-related luminescent centers upon indirect excitation of near-UV light has been synthesized under reducing condition. Steady-state and time-resolved photoluminescence and diffuse reflectance spectra are measured to investigate properties of the luminescence. The results suggest that there is a prominent energy transfer from ZnO host to Eu³⁺ ions. A series of shallow donor energy levels as temporary storage of excitation energy play a crucial role on this energy transfer process. The energy transfer efficiency can be enhanced by these additional shallow donors. Two kinds of local environments for Eu³⁺ in Eu³⁺-Li⁺-codoped ZnO:Zn are distinguished based on the emission and excitation spectra in comparison with pure Eu₂O₃. Such phosphor will be a promising candidate employed in the white light-emitting diodes based on the near-UV pumping.