Organic electroluminescent device
An organic EL device includes at least a light-emitting layer provided between a pair of electrodes. The light-emitting layer includes at least a hole transporting host material and an electron transporting phosphorescent material, and the concentration of the electron transporting phosphorescent material in the light-emitting layer decreases from a cathode side toward an anode side.
1. An organic electroluminescent device comprising at least a light-emitting layer between a pair of electrodes, wherein the light-emitting layer includes at least a hole transporting host material and an electron transporting phosphorescent material, and the concentration of the electron transporting phosphorescent material in the light-emitting layer decreases from a cathode side toward an anode side,
wherein the electron transporting phosphorescent material is a platinum complex according to formula Pt-1:
2. The organic electroluminescent device according to claim 1 , wherein the concentration of the electron transporting phosphorescent material at a region adjacent to an anode side interface of the light-emitting layer is from 0% by mass to 50% by mass with respect to the concentration of the electron transporting phosphorescent material at a region adjacent to a cathode side interface of the light-emitting layer.
3. The organic electroluminescent device according to claim 2 , wherein the concentration of the electron transporting phosphorescent material in the light-emitting layer is 10% by mass or less at the region adjacent to the anode side interface.
4. The organic electroluminescent device according to claim 2 , wherein the concentration of the electron transporting phosphorescent material in the light-emitting layer is 12% by mass or more at the region adjacent to the cathode side interface.
5. The organic electroluminescent device according to claim 1 , wherein the hole transporting host material is a carbazole derivative or an indole derivative.
6. The organic electroluminescent device according to claim 5 , wherein the hole transporting host material is 1,3-bis(carbazole-9-yl)benzene or a derivative thereof.
7. The organic electroluminescent device according to claim 1 , wherein a peak wavelength of a light emission spectrum is 430 nm or more but less than 480 nm.