An organic electroluminescent device having an emission layer, which is constructed with a host, a phosphorescence emission molecule as a dopant, and a fluorescence supporter. The fluorescence supporter receives energy from the host or traps energy directly, and then transfers the energy to the dopant or self-emits light. An emission spectrum of the fluorescence supporter and an absorption spectrum of the phosphorescence emission molecule overlap partly or completely. The organic electroluminescent device has improved luminous efficiency and color purity characteristics in comparison with a conventional organic electroluminescent device having an emission layer, which is composed of a phosphorescent dopant and a host. This system is useful in the manufacture of, in particular, blue emission devices.