US Patent 7709102 Organic electroluminescence device

An organic electroluminescence device comprising a pair of electrodes and a layer of an organic light emitting medium disposed between the pair of electrodes, wherein the layer of an organic light emitting medium comprises a mixed layer comprising (A) at least one hole transporting compound and (B) at least one electron transporting compound, an energy gap of the hole transporting compound represented by Eg1 and an energy gap of the electron transporting compound represented by Eg2 satisfy a relation: Eg1<Eg2. Electrons and holes are recombined in the layer of an organic light emitting medium and light is emitted. The organic electroluminescence device has a long life and emits light at a high efficiency.