Light-emitting element, lighting device, light-emitting device, and electronic device

Patent metadata

Field	Value
Publication number	US-9368741-B2
Application number	US-201414276467-A
Country	US
Kind code	B2
Filing date	May 13, 2014
Priority date	May 17, 2013
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

A light-emitting element includes a first electrode; a first light-emitting layer over the first electrode, containing a first phosphorescent compound and a first host material; a second light-emitting layer over the first light-emitting layer, containing a second phosphorescent compound and a second host material; a third light-emitting layer over the second light-emitting layer, containing a third phosphorescent compound and a third host material; and a second electrode over the third light-emitting layer. Between peaks of emission spectra of the first, second, and third phosphorescent compounds, the peak of the emission spectrum of the second phosphorescent compound is on the longest wavelength side and that of the emission spectrum of the third phosphorescent compound is on the shortest wavelength side. The third host material has higher triplet excitation energy than the first host material and the second host material.

First claim

What is claimed is:

1. A light-emitting element comprising:
a first electrode:
a first light-emitting layer over the first electrode, the first light-emitting layer comprising a first phosphorescent compound and a first host material;
a second light-emitting layer over the first light-emitting layer, the second light-emitting layer comprising a second phosphorescent compound and a second host material;
a third light-emitting layer over the second light-emitting layer, the third light-emitting layer comprising a third phosphorescent compound and a third host material; and
a second electrode over the third light-emitting layer,
wherein between a peak of an emission spectrum of the first phosphorescent compound, a peak of an emission spectrum of the second phosphorescent compound, and a peak of an emission spectrum of the third phosphorescent compound, the peak of the emission spectrum of the second phosphorescent compound is on a longest wavelength side and the peak of the emission spectrum of the third phosphorescent compound is on a shortest wavelength side, and
wherein the third host material has higher triplet excitation energy than the first host material and the second host material.

2. The light-emitting element according to claim 1 ,
wherein the first phosphorescent compound emits green light,
wherein the second phosphorescent compound emits red light, and
wherein the third phosphorescent compound emits blue light.

3. The light-emitting element according to claim 1 ,
wherein the first host material, the second host material, and the third host material each have an electron-transport property when the first electrode functions as an anode.

4. The light-emitting element according to claim 1 ,
wherein the first host material, the second host material, and the third host material each have a hole-transport property when the first electrode functions as a cathode.

5. The light-emitting element according to claim 1 ,
wherein the first host material, the second host material, and the third host material each have a hole-transport property and an electron-transport property, and
wherein the first host material, the second host material, and the third host material each comprise a hole-transport skeleton and an electron-transport skeleton.

6. The light-emitting element according to claim 1 ,
wherein the first host material is the same as the second host material.

7. The light-emitting element according to claim 1 ,
wherein the first light-emitting layer comprises a first carrier-transport compound,
wherein one of the first host material and the first carrier-transport compound has a hole-transport property,
wherein the other of the first host material and the first carrier-transport compound has an electron-transport property,
wherein the second light-emitting layer comprises a second carrier-transport compound,
wherein one of the second host material and the second carrier-transport compound has a hole-transport property,
wherein the other of the second host material and the second carrier-transport compound has an electron-transport property,
wherein the third light-emitting layer comprises a third carrier-transport compound,
wherein one of the third host material and the third carrier-transport compound has a hole-transport property, and
wherein the other of the third host material and the third carrier-transport compound has an electron-transport property.

8. The light-emitting element according to claim 1 ,
wherein the second light-emitting layer has a thickness greater than or equal to 2 nm and less than or equal to 20 nm.

9. The light-emitting element according to claim 1 ,
wherein the second light-emitting layer is in contact with the first light-emitting layer and the third light-emitting layer.

10. A lighting device comprising the light-emitting element according to claim 1 .

11. An electronic device comprising a light-emitting device, the light-emitting device comprising:
the light-emitting element according to claim 1 ; and
a unit for controlling the light-emitting element.

12. A light-emitting element comprising:
a first electrode;
a first light-emitting layer over the first electrode, the first light-emitting layer comprising a first phosphorescent compound and a first host material;
a second light-emitting layer over the first light-emitting layer, the second light-emitting layer comprising a second phosphorescent compound and a second host material;
a third light-emitting layer over the second light-emitting layer, the third light-emitting layer comprising a third phosphorescent compound and a third host material; and
a second electrode over the third light-emitting layer,
wherein the first phosphorescent compound emits green light,
wherein the second phosphorescent compound emits red light, and
wherein the third phosphorescent compound emits blue light.

13. The light-emitting element according to claim 12 ,
wherein the first host material, the second host material, and the third host material each have an electron-transport property when the first electrode functions as an anode.

14. The light-emitting element according to claim 12 ,
wherein the first host material, the second host material, and the third host material each have a hole-transport property when the first electrode functions as a cathode.

15. The light-emitting element according to claim 12 ,
wherein the first host material, the second host material, and the third host material each have a hole-transport property and an electron-transport property, and
wherein the first host material, the second host material, and the third host material each comprise a hole-transport skeleton and an electron-transport skeleton.

16. The light-emitting element according to claim 12 ,
wherein the first host material is the same as the second host material.

17. The light-emitting element according to claim 12 ,
wherein the first light-emitting layer comprises a first carrier-transport compound,
wherein one of the first host material and the first carrier-transport compound has a hole-transport property,
wherein the other of the first host material and the first carrier-transport compound has an electron-transport property,
wherein the second light-emitting layer comprises a second carrier-transport compound,
wherein one of the second host material and the second carrier-transport compound has a hole-transport property,
wherein the other of the second host material and the second carrier-transport compound has an electron-transport property,
wherein the third light-emitting layer comprises a third carrier-transport compound,
wherein one of the third host material and the third carrier-transport compound has a hole-transport property and
wherein the other of the third host material and the third carrier-transport compound has an electron-transport property.

18. The light-emitting element according to claim 12 ,
wherein the second light-emitting layer has a thickness greater than or equal to 2 nm and less than or equal to 20 nm.

19. The light-emitting element according to claim 12 ,
wherein the second light-emitting layer is in contact with the first light-emitting layer and the third light-emitting layer.

20. A lighting device comprising the light-emitting element according to claim 12 .

21. An electronic device comprising a light-emitting device, the light-emitting device comprising:
the light-emitting element according to claim 12 ; and
a uni

Assignees

• Semiconductor Energy Lab

Inventors

• Ishisone Takahiro
• Seo Satoshi

Classifications

• C09K2211/185

  of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd · CPC title

• C07F15/0033

  Iridium compounds · CPC title

• C09K2211/1059

  containing three nitrogen atoms as heteroatoms · CPC title

• C09K11/06 Primary

  containing organic luminescent materials · CPC title

• C09K2211/1007

  Non-condensed systems · CPC title