| 摘要 |
An organic electroluminescent device excellent in luminescence lifetime which comprises as the essentials a cathode and an anode which are opposite to each other and a light-emitting layer between the cathode and the anode which contains both a host material and a dopant material, characterized in that the dopant material is represented by the general formula (1) and the concentration of the dopant material lowers in the thickness direction of the light-emitting layer from the anode side to the cathode side: wherein R<SUB>1</SUB> is a substituent; Z is a nonmetal atomic group necessary for the formation of a 5- to 7-membered ring; n1 is an integer of 0 to 5; B<SUB>1</SUB> to B<SUB>5</SUB> are each carbon, nitrogen, oxygen, or sulfur, at least one of them being nitrogen; M<SUB>1</SUB> is a member selected from among Group 8 to 10 metals of the periodic table; X<SUB>1</SUB> and X<SUB>2</SUB> are each carbon, nitrogen, or oxygen; and L<SUB>1</SUB> is an atomic group capable of forming together with X<SUB>1</SUB> and X<SUB>2</SUB> a bidentate ligand. |
