LIGHT-EMITTING ELEMENT, LIGHT-EMITTING DEVICE, ELECTRONIC APPLIANCE, AND LIGHTING DEVICE

• US 20150155510A1
• Filed: 11/20/2014
• Published: 06/04/2015
• Est. Priority Date: 12/02/2013
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kawata, Takuya, Ohsawa, Nobuharu, Nonaka, Yusuke, Ishisone, Takahiro, Seo, Satoshi
• Granted Patent: US 9,368,742 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent 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 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 77/111 Flexible substrates
• 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 85/622 containing four rings, e.g. pyrene
• CPC Class Codes: H10K 85/626 containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• 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
• CPC Class Codes: Y02E 10/549 Organic PV cells

Abstract

A light-emitting element includes a stack of a first light-emitting layer emitting fluorescent light and a second light-emitting layer emitting phosphorescent light between a pair of electrodes. The second light-emitting layer includes a first layer in which an exciplex is formed, a second layer in which an exciplex is formed, and a third layer in which an exciplex is formed. The second layer is located over the first layer, and the third layer is located over the second layer. An emission peak wavelength of the second layer is longer than an emission peak wavelength of the first layer and an emission peak wavelength of the third layer.

Claims

1. A light-emitting element comprising:

a stack of a first light-emitting layer emitting fluorescent light and a second light-emitting layer emitting phosphorescent light, the stack being between a pair of electrodes,

wherein the second light-emitting layer comprises a first layer in which an exciplex is formed, a second layer in which an exciplex is formed, and a third layer in which an exciplex is formed,

wherein the second layer is located over the first layer, and the third layer is located over the second layer,

wherein the second layer is in contact with the first layer and the third layer, and

wherein an emission peak wavelength of the second layer is longer than an emission peak wavelength of the first layer and an emission peak wavelength of the third layer.

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

wherein the first light-emitting layer and the second light-emitting layer are in contact with each other.

3. A light-emitting device comprising:

a pixel portion comprising the light-emitting element according to claim 1;

a driver circuit electrically connected to the pixel portion; and

a flexible printed circuit electrically connected to the driver circuit.

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

5. A light-emitting element comprising:

a stack of a first light-emitting layer and a second light-emitting layer, the stack being between a pair of electrodes,

wherein the first light-emitting layer contains a fluorescent substance,

wherein the second light-emitting layer comprises a first layer, a second layer over the first layer, and a third layer over the second layer,

wherein each of the first layer, the second layer, and the third layer contains a phosphorescent substance,

wherein an emission peak wavelength of the second layer is longer than an emission peak wavelength of the first layer and an emission peak wavelength of the third layer, and

wherein the first light-emitting layer and the second light-emitting layer are in contact with each other.

6. The light-emitting element according to claim 5,

wherein the second layer is in contact with the first layer and the third layer.

7. The light-emitting element according to claim 5,

wherein each of the first layer, the second layer, and the third layer contains substances forming an exciplex.

8. The light-emitting element according to claim 5,

wherein the first layer and the third layer contain the same substances forming an exciplex, and

wherein the phosphorescent substance in the first layer and the phosphorescent substance in the third layer are the same phosphorescent substance.

9. The light-emitting element according to claim 5,

wherein first layer, the second layer, and the third layer contain the same substances forming an exciplex.

10. The light-emitting element according to claim 5,

wherein the first light-emitting layer contains a host material, and

wherein a T1 level of the host material is lower than a T1 level of the fluorescent substance.

11. A light-emitting device comprising:

a pixel portion comprising the light-emitting element according to claim 5;

a driver circuit electrically connected to the pixel portion; and

a flexible printed circuit electrically connected to the driver circuit.

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

13. A light-emitting element comprising:

a stack of a first light-emitting layer and a second light-emitting layer, the stack being between a pair of electrodes,

wherein the first light-emitting layer contains a fluorescent substance,

wherein the second light-emitting layer comprises a first layer, a second layer over the first layer, and a third layer over the second layer,

wherein each of the first layer, the second layer, and the third layer contains a phosphorescent substance,

wherein an emission peak wavelength of the second layer is longer than an emission peak wavelength of the first layer and an emission peak wavelength of the third layer, and

wherein an emission peak wavelength of the first layer of the second light-emitting layer is longer than an emission peak wavelength of the first light-emitting layer.

14. The light-emitting element according to claim 13,

wherein the second layer is in contact with the first layer and the third layer.

15. The light-emitting element according to claim 13,

wherein the first light-emitting layer and the second light-emitting layer are in contact with each other.

16. The light-emitting element according to claim 13,

wherein each of the first layer, the second layer, and the third layer contains substances forming an exciplex.

17. The light-emitting element according to claim 13,

wherein the first layer and the third layer contain the same substances forming an exciplex, and

wherein the phosphorescent substance in the first layer and the phosphorescent substance in the third layer are the same phosphorescent substance.

18. The light-emitting element according to claim 13,

wherein first layer, the second layer, and the third layer contain the same substances forming an exciplex.

19. The light-emitting element according to claim 13,

wherein the first light-emitting layer contains a host material, and

wherein a T1 level of the host material is lower than a T1 level of the fluorescent substance.

20. The light-emitting element according to claim 13,

wherein the first light-emitting layer emits blue light,

wherein the first layer of the second light-emitting layer emits green light,

wherein the second layer of the second light-emitting layer emits red light, and

wherein the third layer of the second light-emitting layer emits green light.

21. A light-emitting device comprising:

a pixel portion comprising the light-emitting element according to claim 13;

a driver circuit electrically connected to the pixel portion; and

a flexible printed circuit electrically connected to the driver circuit.

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