Light-emitting element

Patent metadata

Field	Value
Publication number	US-10586934-B2
Application number	US-201916261698-A
Country	US
Kind code	B2
Filing date	Jan 30, 2019
Priority date	Feb 16, 2011
Publication date	Mar 10, 2020
Grant date	Mar 10, 2020

Abstract

A light-emitting element having high external quantum efficiency is provided. A light-emitting element having a long lifetime is provided. A light-emitting element is provided which includes a light-emitting layer containing a phosphorescent compound, a first organic compound, and a second organic compound between a pair of electrodes, in which a combination of the first organic compound and the second organic compound forms an exciplex (excited complex). The light-emitting element transfers energy by utilizing an overlap between the emission spectrum of the exciplex and the absorption spectrum of the phosphorescent compound and thus has high energy transfer efficiency. Therefore, a light-emitting element having high external quantum efficiency can be obtained.

First claim

The invention claimed is:

1. A light-emitting element comprising:
a pair of electrodes; and
a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,
wherein the first organic compound and the second organic compound are selected so as to form an exciplex,
wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,
wherein one of the first organic compound and the second organic compound is a carbazole compound,
wherein the carbazole compound comprises a carbazol-3-yl group, and
wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

2. The light-emitting element according to claim 1 ,
wherein the first organic compound is a heterocyclic compound.

3. The light-emitting element according to claim 1 , further comprising:
a hole injection layer,
wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

4. The light-emitting element according to claim 1 , further comprising:
a hole transport layer,
wherein the hole transport layer comprises an aromatic amine compound, and
wherein the aromatic amine compound comprises a fluorenyl group.

5. The light-emitting element according to claim 1 ,
wherein one of the electrodes comprises ytterbium.

6. The light-emitting element according to claim 1 ,
wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

7. The light-emitting element according to claim 1 ,
wherein the longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

8. The light-emitting element according to claim 1 ,
wherein a level of a triplet excitation energy of each of the first organic compound and second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.

9. The light-emitting element according to claim 1 ,
wherein one of the first organic compound and the second organic compound has higher content than the other, and
wherein a phosphorescence spectrum of the one overlaps with the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

10. A light-emitting element comprising:
a pair of electrodes; and
a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,
wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,
wherein one of the first organic compound and the second organic compound is a carbazole compound,
wherein the carbazole compound comprises a first carbazole ring and a second cabazole ring,
wherein the first carbazole ring at 3-position bonds to the second carbazole ring at 3-position, and
wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

11. The light-emitting element according to claim 10 ,
wherein the first organic compound is a heterocyclic compound.

12. The light-emitting element according to claim 10 , further comprising:
a hole injection layer,
wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

13. The light-emitting element according to claim 10 , further comprising:
a hole transport layer,
wherein the hole transport layer comprises an aromatic amine compound, and
wherein the aromatic amine compound comprises a fluorenyl group.

14. The light-emitting element according to claim 10 ,
wherein one of the electrodes comprises ytterbium.

15. The light-emitting element according to claim 10 ,
wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

16. The light-emitting element according to claim 10 ,
wherein the longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

17. The light-emitting element according to claim 10 ,
wherein a level of a triplet excitation energy of each of the first organic compound and second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.

18. The light-emitting element according to claim 10 ,
wherein one of the first organic compound and the second organic compound has higher content than the other, and
wherein a phosphorescence spectrum of the one overlaps with the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

19. A light-emitting element comprising:
a pair of electrodes; and
a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,
wherein the first organic compound and the second organic compound are selected so as to form an exciplex,
wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,
wherein one of the first organic compound and the second organic compound is a carbazole compound,
wherein the carbazole compound comprises two cabazole rings, and
wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

20. The light-emitting element according to claim 19 ,
wherein the two cabazole rings directly bond to each other.

21. The light-emitting element according to claim 19 ,
wherein the first organic compound is a heterocyclic compound.

22. The light-emitting element according to claim 19 , further comprising:
a hole injection layer,
wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

23. The light-emitting element according to claim 19 , further comprising:
a hole transport layer,
wherein the hole transport layer comprises an aromatic amine compound, and
wherein the aromatic amine compound comprises a fluorenyl group.

24. The light-emitting element according to claim 19 ,
wherein one of the electrodes comprises ytterbium.

25. The light-emitting element according to claim 19 ,
wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

26. The light-emitting element according to claim 19 ,
wherei

Assignees

• Semiconductor Energy Lab

Inventors

• Shitagaki Satoko
• Seo Satoshi
• Ohsawa Nobuharu
• Inoue Hideko
• Suzuki Kunihiko

Classifications

• C07D409/10

  linked by a carbon chain containing aromatic rings · CPC title

• C09K11/025

  non-luminescent particle coatings or suspension media · CPC title

• C07D241/12

  with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms · CPC title

• C07D239/26 Primary

  with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms · CPC title

• C07D471/04

  Ortho-condensed systems · CPC title