Patent ID: 8872423

Claim:
An electroluminescent device comprising: an anode; a cathode; and an organic layer held between said anode and said cathode, the organic layer including a light-emitting layer, a hole supply layer arranged between said anode and the light-emitting layer and having a thickness ranging from 30 to 40 nm, the hole supply layer including a hole injection layer and a hole transport layer, and an electron supply layer containing at least one layer including a nitrogen-containing heterocycle derivative that is a benzimidazole derivative that is arranged between said cathode and said light-emitting layer, the electron supply layer having a thickness greater than a combined thickness of the hole supply layer and the light-emitting layer, wherein the electron supply layer and said organic layer are formed to satisfy the following relationship: 0.90 >d 1 /d 2 >0.30 where d 1 is the thickness of the electron supply layer and d 2 is a thickness of said organic layer, wherein a combined thickness of the at least one layer including the nitrogen-containing heterocycle derivative ranges from 70 nm to 130 nm, and wherein the electroluminescent device has a current efficiency of at least 6.0 cd/A.