Abstract: By vacuum evaporation deposition, dye-doped OLEDs were fabricated with the structure of ITO/TPD/ZnQ2: Rhodamine B(RhB)/Al. The luminescent layer was composed of a dye RhB doped into ZnQ2 (bis (8-hydroxyquinolato) zinc) layer which showed much better electroluminescent properties than AlQ3(tri (8-hydroxyquinolato) aluminum). With different RhB concentration, OLED electroluminescence emission got different peak wavelength and visual color. The maximal shift of 34 nm was obtained due to dopant concentration. By investigating photoluminescence as well as electroluminescence behaviors, the energy transfer mode and emission mechanism were discussed in this paper. Both energy transfer and carrier trapping have been suggested to be responsible for dopant excitation and emission.