Patent ID: 7560729

Claim:
An organic electroluminescent device having an anode, a cathode, and a plurality of organic compound layers provided between the anode and the cathode and including a light-emitting layer, and three or more organic compound layers provided between the light-emitting layer and the anode, or between the light-emitting layer and the cathode; wherein the light-emitting layer contains a host material and at least two light-emitting materials, and wherein the at least two light-emitting materials include a phosphorescent light-emitting material, and wherein three or more organic compound layers are provided between the light-emitting layer and the anode, the formula (1): Ip 1 >Ip 2 >Ip 3 > . . . >Ipn is satisfied, wherein Ip 1 is the ionization potential of the light-emitting layer, and the ionization potentials of the three or more organic compound layers are Ip 2 , Ip 3 , . . . , and Ipn in the order starting from the light-emitting layer, wherein n is an integer of 4 or more, or wherein three or more organic compound layers are provided between the light-emitting layer and the cathode, the formula (2): Ea 1 <Ea 2 <Ea 3 < . . . <Eam is satisfied, wherein Ea 1 is the electron affinity of the light-emitting layer, and the electron affinities of the three or more organic compound layers are Ea 2 , Ea 3 , . . . , and Eam in the order starting from the light-emitting layer, wherein m is an integer of 4 or more.