Organic electric field light-emitting element

1. An organic electric field light-emitting element, comprising:

an anode;

a cathode; and

a light-emitting layer provided between the anode and the cathode,

wherein the light-emitting layer contains two or more luminescent materials each giving a different emission peak, and a concentration ratio [(B/A)×100] in the light-emitting layer gradually increases along with the direction from an anode side of the light-emitting layer to a cathode side of the light-emitting layer, where the concentration ratio [(B/A)×100] is a concentration ratio of the luminescent materials, and A denotes a concentration of the luminescent material having the emission peak at the shortest wavelength side compared to the emission peaks of other luminescent materials, and B denote a concentration of the luminescent material having the emission peak at the longest wavelength side compared to the emission peaks of other luminescent materials, and

wherein the light-emitting layer satisfies the relationship of: [(B/A)×100]≦10%.

2. The organic electric field light-emitting element according to claim 1 , wherein B is constant and A decreases along with the direction from the anode side to the cathode side.

3. The organic electric field light-emitting element according to claim 1 , wherein B increases along with the direction from the anode side to the cathode side, and A is constant.

4. The organic electric field light-emitting element according to claim 1 , wherein B increases and A decreases along with the direction from the anode side to the cathode side.

5. The organic electric field light-emitting element according to claim 1 , wherein the light-emitting layer satisfies the relationship of: a/b>1.05, where a denotes B/A at the cathode side of the light-emitting layer, and b denotes B/A at the anode side of the light-emitting layer.

6. The organic electric field light-emitting element according to claim 1 , wherein the light-emitting layer has a thickness of 20 nm or more.

7. The organic electric field light-emitting element according to claim 1 , wherein the cathode is a reflecting electrode, and the anode is a transparent is electrode.

8. The organic electric field light-emitting element according to claim 1 , wherein the cathode is a reflecting electrode, and the anode is a translucent electrode.

9. The organic electric field light-emitting element according to claim 1 , wherein the luminescent materials are phosphorescent materials.

10. An organic electric field light-emitting element, comprising:

an anode;

a cathode; and

a light-emitting layer provided between the anode and the cathode,

wherein the light-emitting layer contains a luminescent material whose monomer and association each give a different emission peak,

wherein a ratio of a concentration of the association of the luminescent material to a concentration of the monomer of the luminescent material gradually increases along with the direction from an anode side of the light-emitting layer to a cathode side of the light-emitting layer, and

wherein the light-emitting layer satisfies an intensity ratio [(D/C)×100] of 20% or larger, where C denotes an integral spectrum intensity of the monomer and D denotes an integral spectrum intensity of the association.

11. The organic electric field light-emitting element according to claim 10 , wherein the concentration of the association is constant, and the concentration of the monomer decreases along with the direction from the anode side to the cathode side, where the emission peak of the association is present at longer wavelength side compared to the emission peak of the monomer, and the emission peak of the monomer is present at shorter wavelength side compared to the emission peak of the association.

12. The organic electric field light-emitting element according to claim 10 , wherein the concentration of the association increases along with the direction from the anode side to the cathode side, and the concentration of the monomer is constant, where the emission peak of the association is present at longer wavelength side compared to the emission peak of the monomer, and the emission peak of the monomer is present at shorter wavelength side compared to the emission peak of the association.

13. The organic electric field light-emitting element according to claim 10 , wherein the concentration of the association increases and the concentration of the monomer decreases along with the direction from the anode side to the cathode side, where the emission peak of the association is present at longer wavelength side compared to the emission peak of the monomer, and the emission peak of the monomer is present at shorter wavelength side compared to the emission peak of the association.

14. The organic electric field light-emitting element according to claim 10 , wherein the light-emitting layer satisfies the relationship of: a/b>1.05, where a denotes the ratio of the concentration of the association to the concentration of the monomer at the cathode side of the light-emitting layer, and b denotes the ratio of the concentration of the association to the concentration of the monomer at the anode side of the light-emitting layer, and wherein the emission peak of the association is present at longer wavelength side compared to the emission peak of the monomer, and the emission peak of the monomer is present at shorter wavelength side compared to the emission peak of the association.

15. The organic electric field light-emitting element according to claim 10 , wherein the light-emitting layer has a thickness of 20 nm or more.

16. The organic electric field light-emitting element according to claim 10 , wherein the cathode is a reflecting electrode, and the anode is a transparent electrode.

17. The organic electric field light-emitting element according to claim 10 , wherein the cathode is a reflecting electrode, and the anode is a translucent electrode.

18. The organic electric field light-emitting element according to claim 10 , wherein the luminescent material is a phosphorescent material.