Light-emitting element

• US 10,593,895 B2
• Filed: 03/09/2017
• Issued: 03/17/2020
• Est. Priority Date: 02/16/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Shitagaki, Satoko, Seo, Satoshi, Ohsawa, Nobuharu, Inoue, Hideko, Suzuki, Kunihiko
• Primary Examiner(s): Rahman, Moin M
• Application Number:
  US15/454,055
• Publication Number:
  US 20170179411A1
• Time in Patent Office: 1,104 Days
• Field of Search: 438 22- 47, 438 69, 438493, 438503, 438507, 438956, 257 13, 257 79-103, 257918, 257 40, 257642-643, 257759
• CPC Class Codes: C07D 209/86 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to carbon atoms of the ring system
• CPC Class Codes: C07D 239/26 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• CPC Class Codes: C07D 241/12 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• CPC Class Codes: C07D 333/76 Dibenzothiophenes
• CPC Class Codes: C07D 409/10 linked by a carbon chain containing aromatic rings
• CPC Class Codes: C07D 471/04 Ortho-condensed systems
• CPC Class Codes: C07F 15/0033 Iridium compounds
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1007 Non-condensed systems
• CPC Class Codes: C09K 2211/1074 containing more than three nitrogen atoms as heteroatoms
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/90 Multiple hosts in the emissive layer
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• 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 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.

Claims

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, and

wherein a difference between an energy value of a peak of the emission spectrum of the exciplex and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound is 0.3 eV or less.

2. The light-emitting element according to claim 1, wherein the first organic compound, the second organic compound, and the phosphorescent compound are mixed in the light-emitting layer.

3. The light-emitting element according to claim 1, wherein the phosphorescent compound is an organometallic complex.

4. 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.

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

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

7. The light-emitting element according to claim 1, wherein an energy of the exciplex can be transferred to the phosphorescent compound from the exciplex.

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

9. A light-emitting element comprising:

a first electrode;

a first light-emitting layer over the first electrode;

a charge-generation layer over the first light-emitting layer;

a second light-emitting layer over the charge-generation layer; and

a second electrode over the second light-emitting layer,

wherein at least one of the first light-emitting layer and the second light-emitting layer comprises a phosphorescent compound, a first organic compound, and a second organic compound,

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, and

wherein a difference between an energy value of a peak of the emission spectrum of the exciplex and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound is 0.3 eV or less.

10. The light-emitting element according to claim 9, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound is 0.2 eV or less.

11. The light-emitting element according to claim 9, wherein an energy of the exciplex can be transferred to the phosphorescent compound from the exciplex.

12. The light-emitting element according to claim 9, wherein each of a level of a triplet excitation energy of the first organic compound and a level of a triplet excitation energy of the second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.

13. The light-emitting element according to claim 9, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound is 0.1 eV or less.

14. The light-emitting element according to claim 9, wherein the other one of the first light-emitting layer and the second light-emitting layer comprises a fluorescent material.

15. The light-emitting element according to claim 9, wherein an emission color of the first light-emitting layer and an emission color of the second light-emitting layer are complementary.

16. 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, and

wherein a difference between an energy value of a peak of the emission spectrum of the exciplex and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound is 0.2 eV or less.

17. The light-emitting element according to claim 16, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound is 0.1 eV or less.

18. The light-emitting element according to claim 16, wherein the first organic compound, the second organic compound, and the phosphorescent compound are mixed in the light-emitting layer.

19. The light-emitting element according to claim 16, wherein the phosphorescent compound is an organometallic complex.

20. The light-emitting element according to claim 16, wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

21. An electronic device comprising the light-emitting element according to claim 16.

22. A lighting device comprising the light-emitting element according to claim 16.

23. The light-emitting element according to claim 16, wherein an energy of the exciplex can be transferred to the phosphorescent compound from the exciplex.

24. The light-emitting element according to claim 16, wherein each of a level of a triplet excitation energy of the first organic compound and a level of a triplet excitation energy of the second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.