Patent ID: 8778507

Claim:
An organic electroluminescent device comprising: a light emission layer containing a) two or more kinds of host compounds, wherein two of the two or more host compounds are Host A, and Host B, different from Host A, and b) Dopant D, wherein the dopant D emits blue light, and at least one of the Host A and Host B has an excited triplet energy of not less than 2.70 eV, and the Dopant D is a phosphorescent compound selected from an iridium complex comprising only bidentate ligands and a platinum complex comprising only bidentate ligands, each of Host A and Host B being selected from compounds having a partial structure of one to three carbazole rings represented by Formula (2) and compounds having a partial structure of one to three azacarbazole rings represented by Formula (3), wherein R 21 through R 28 independently represent a hydrogen atom, an aromatic hydrocarbon group or an aromatic heterocyclic group; and R 29 represents a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group, the substituent of the substituted aromatic hydrocarbon group or aromatic heterocyclic group being selected from an alkyl group, a cycloalkyl group, an aromatic hydrocarbon ring group and an aromatic heterocyclic group, wherein X 31 through X 38 independently represent a carbon atom or a nitrogen atom, provided that any one of X 31 through X 38 is a nitrogen atom; any of R 31 through R 38 bonding to the carbon atom independently represents a hydrogen atom, an aromatic hydrocarbon group or an aromatic heterocyclic group; any one of R 31 through R 38 bonding to the nitrogen atom represents a lone electron pair; and R 39 represents a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group, the substituent of the substituted aromatic hydrocarbon group or aromatic heterocyclic group being selected from an alkyl group, a cycloalkyl group, an aromatic hydrocarbon ring group and an aromatic heterocyclic group, wherein the following relationships are satisfied: |LUMO- A |<|LUMO- D |<|LUMO- B |, and |HOMO- A |<|HOMO- D |<|HOMO- B| wherein HOMO-A and HOMO-B represent energy level of HOMO of Host A and energy level of HOMO of Host B, respectively; LUMO-A and LUMO-B represent energy level of LUMO of Host A and energy level of LUMO of Host B, respectively; and HOMO-D and LUMO-D represent energy level of HOMO of Dopant D and energy level LUMO of Dopant D, respectively.