Light-emitting element

• US 9,175,213 B2
• Filed: 03/14/2012
• Issued: 11/03/2015
• Est. Priority Date: 03/23/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Satoshi, Shitagaki, Satoko, Ohsawa, Nobuharu, Inoue, Hideko, Suzuki, Kunihiko
• Primary Examiner(s): Breval, Elmito
• Application Number:
  US13/419,892
• Publication Number:
  US 20120242219A1
• Time in Patent Office: 1,329 Days
• Field of Search: 313500-512
• US Class Current: 1/1
• CPC Class Codes: C07D 409/10 linked by a carbon chain containing aromatic rings
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1007 Non-condensed systems
• CPC Class Codes: C09K 2211/1011 Condensed systems
• CPC Class Codes: C09K 2211/1029 containing one nitrogen atom as the heteroatom
• CPC Class Codes: C09K 2211/1044 containing two nitrogen atoms as heteroatoms
• CPC Class Codes: C09K 2211/1088 containing oxygen as the only heteroatom
• CPC Class Codes: C09K 2211/1092 containing sulfur as the only heteroatom
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/121 for assisting energy transfer, e.g. sensitization
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/624 containing six or more rings
• CPC Class Codes: H10K 85/626 containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/633 comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/636 comprising heteroaromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/6572 comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
• CPC Class Codes: H10K 85/6576 : comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene

Abstract

A light-emitting element having high external quantum efficiency is provided. A light-emitting element having low drive voltage is provided. Provided is a light-emitting element which includes a light-emitting layer containing a phosphorescent compound, a first organic compound, and a second organic compound between a pair of electrodes. A combination of the first organic compound and the second organic compound forms an exciplex (excited complex). An emission spectrum of the exciplex overlaps with an absorption band located on the longest wavelength side of an absorption spectrum of the phosphorescent compound. A peak wavelength of the emission spectrum of the exciplex is longer than or equal to a peak wavelength of the absorption band located on the longest wavelength side of the absorption spectrum of the phosphorescent compound.

Claims

1. A light-emitting element comprising:

a light-emitting layer comprising a phosphorescent compound, a first organic compound, and a second organic compound,

wherein the first organic compound and the second organic compound are configured to form an exciplex, and

wherein an emission peak wavelength of the exciplex is longer than or equal to a peak wavelength of an absorption of a triplet metal to ligand charge transfer transition of the phosphorescent compound.

2. The light-emitting element according to claim 1,

wherein excitation energy of the exciplex is transferred to the phosphorescent compound so that the phosphorescent compound emits phosphorescence.

3. The light-emitting element according to claim 1,

wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

4. The light-emitting element according to claim 1,

wherein the phosphorescent compound is an organometallic complex.

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

6. A lighting device comprising the light-emitting device according to claim 5.

7. An electronic device comprising the light-emitting device according to claim 5.

8. A light-emitting element comprising:

a light-emitting layer comprising a phosphorescent compound, a first organic compound, and a second organic compound,

wherein the first organic compound and the second organic compound are configured to form an exciplex,

wherein an emission peak wavelength of the exciplex is longer than or equal to a peak wavelength of an absorption of a triplet metal to ligand charge transfer transition of the phosphorescent compound, and

wherein a difference between the emission peak wavelength of the exciplex and the peak wavelength of the absorption of the triplet metal to ligand charge transfer transition of the phosphorescent compound is 30 nm or less.

9. The light-emitting element according to claim 8,

wherein excitation energy of the exciplex is transferred to the phosphorescent compound so that the phosphorescent compound emits phosphorescence.

10. The light-emitting element according to claim 8,

wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

11. The light-emitting element according to claim 8,

wherein the phosphorescent compound is an organometallic complex.

12. A light-emitting device comprising the light-emitting element according to claim 8.

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

14. An electronic device comprising the light-emitting device according to claim 12.

15. A light-emitting element comprising:

a light-emitting layer comprising a phosphorescent compound, a first organic compound, and a second organic compound,

wherein the first organic compound and the second organic compound are configured to form an exciplex, and

wherein an emission peak wavelength of the exciplex is longer than or equal to a peak wavelength of an absorption of a triplet metal-to-ligand charge transfer transition of the phosphorescent compound and shorter than or equal to an emission peak wavelength of the phosphorescent compound.

16. The light-emitting element according to claim 15,

wherein a difference between the emission peak wavelength of the exciplex and the emission peak wavelength of the phosphorescent compound is 30 nm or less.

17. The light-emitting element according to claim 15,

wherein excitation energy of the exciplex is transferred to the phosphorescent compound so that the phosphorescent compound emits phosphorescence.

18. The light-emitting element according to claim 15,

wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

19. The light-emitting element according to claim 15,

wherein the phosphorescent compound is an organometallic complex.

20. A light-emitting device comprising the light-emitting element according to claim 15.

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

22. An electronic device comprising the light-emitting device according to claim 20.