IP Library › Granted Patent US 10,693,095

Granted Patent B2

US 10,693,095 · App. 15/874,950 · Granted Jun 23, 2020

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

Inventors: Satoshi Seo (Kanagawa, JP); Nobuharu Ohsawa (Kanagawa, JP); Shunsuke Hosoumi (Kanagawa, JP); Takahiro Ishisone (Kanagawa, JP)

Assignee: Semiconductor Energy Laboratory Co., Ltd.

H01L51/5016 H01L51/5012 H01L2251/552

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Quick Facts

Patent No.: US 10,693,095
App. No.: 15/874,950
Granted: Jun 23, 2020
Kind: B2

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Abstract

A light-emitting element having high emission efficiency which includes a fluorescent material as a light-emitting substance is provided. A light-emitting element includes a pair of electrodes and an EL layer between the pair of electrodes. The EL layer includes a light-emitting layer. The light-emitting layer includes a host material and a guest material. The host material has a difference of more than 0 eV and less than or equal to 0.2 eV between a singlet excitation energy level and a triplet excitation energy level. The guest material is capable of emitting fluorescence. The triplet excitation energy level of the host material is higher than a triplet excitation energy level of the guest material.

Claims (92)

1. A light-emitting element comprising:

a pair of electrodes; and

an electroluminescence layer between the pair of electrodes,

wherein the electroluminescence layer comprises a light-emitting layer,

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

wherein the first material comprises a condensed heterocyclic skeleton having a pyrimidine skeleton,

wherein the second material is capable of emitting fluorescence,

wherein light emitted from the light-emitting layer comprises light emitted from the second material,

wherein light emitted from the light-emitting layer comprises delayed fluorescence,

wherein a triplet excitation energy level of the first material is higher than a triplet excitation energy level of the second material,

wherein the first material is capable of exhibiting thermally activated delayed fluorescence at room temperature,

wherein a singlet excitation energy level of the first material is higher than a singlet excitation energy level of the second material, and

wherein an emission of the first material comprises a region overlapping with an absorption band on a longest wavelength side in an absorption spectrum of the second material.

2. The light-emitting element according to claim 1 , wherein a difference between the singlet excitation energy level and the triplet excitation energy level of the first material is more than 0 eV and less than or equal to 0.2 eV.

3. The light-emitting element according to claim 1 , wherein a weight ratio of the second material to the first material is more than 0 and less than or equal to 0.05.

4. A display device comprising:

the light-emitting element according to claim 1 ; and

a color filter overlapping with the light-emitting element.

5. An electronic device comprising:

the display device according to claim 4 ; and

a housing or a touch sensor.

6. A lighting device comprising:

the light-emitting element according to claim 1 ; and

a housing or a touch sensor.

7. The light-emitting element according to claim 1 , wherein the second material is not capable of exhibiting delayed fluorescence.

8. The light-emitting element according to claim 1 , wherein a difference between the singlet excitation energy level and the triplet excitation energy level in the second material is more than 0.2 eV.

9. The light-emitting element according to claim 1 , wherein the second material comprises any one of an anthracene skeleton or a pyrene skeleton.

10. The light-emitting element according to claim 1 , wherein the first material is a host material,

wherein the second material is a guest material.

11. A light-emitting element comprising:

a pair of electrodes; and

an electroluminescence layer between the pair of electrodes,

wherein the electroluminescence layer comprises a light-emitting layer,

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

wherein the first organic compound comprises a condensed heterocyclic skeleton having a pyrimidine skeleton,

wherein a combination of the first organic compound and the second organic compound is capable of constituting an exciplex,

wherein the third organic compound is capable of emitting fluorescence,

wherein light emitted from the light-emitting layer comprises light emitted from the third organic compound,

wherein light emitted from the light-emitting layer comprises delayed fluorescence, and

wherein a triplet excitation energy level of the exciplex is higher than a triplet excitation energy level of the third organic compound,

wherein the exciplex is capable of exhibiting thermally activated delayed fluorescence at room temperature, and

wherein a singlet excitation energy level of the exciplex is higher than a singlet excitation energy level of the third organic compound.

12. The light-emitting element according to claim 11 , wherein a difference between the singlet excitation energy level and the triplet excitation energy level of the exciplex is more than 0 eV and less than or equal to 0.2 eV.

13. The light-emitting element according to claim 11 , wherein a triplet excitation energy level of each of the first organic compound and the second organic compound is higher than the triplet excitation energy level of the exciplex.

14. The light-emitting element according to claim 11 , wherein an emission spectrum of the exciplex comprises a region overlapping with an absorption band on a longest wavelength side in an absorption spectrum of the third organic compound.

15. The light-emitting element according to claim 11 , wherein a weight ratio of the third organic compound to the combination of the first organic compound and the second organic compound is more than 0 and less than or equal to 0.05.

16. A display device comprising:

the light-emitting element according to claim 11 ; and

a color filter.

17. An electronic device comprising:

the display device according to claim 16 ; and

a housing or a touch sensor.

18. A lighting device comprising:

the light-emitting element according to claim 11 ; and

a housing or a touch sensor.

19. The light-emitting element according to claim 11 , wherein the third organic compound is not capable of exhibiting delayed fluorescence.

20. The light-emitting element according to claim 11 , wherein a difference between the singlet excitation energy level and the triplet excitation energy level in the third organic compound is more than 0.2 eV.

21. The light-emitting element according to claim 11 , wherein the third organic compound comprises any one of an anthracene skeleton or a pyrene skeleton.

22. The light-emitting element according to claim 11 , wherein the second organic compound comprises an aromatic amine skeleton and carbazole skeleton.

23. The light-emitting element according to claim 22 , wherein the aromatic amine skeleton is bonded to 9-position of the carbazole skeleton.

24. A light-emitting element comprising:

a pair of electrodes;

a first electroluminescence layer and a second electroluminescence layer between the pair of electrodes; and

a charge generation layer between the first electroluminescence layer and the second electroluminescence layer,

wherein the first electroluminescence layer comprises a first light-emitting layer,

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