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

Patent metadata

Field	Value
Publication number	US-9911936-B2
Application number	US-201514837083-A
Country	US
Kind code	B2
Filing date	Aug 27, 2015
Priority date	Aug 29, 2014
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

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.

First claim

What is claimed is:

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 host material and a guest material,
wherein the guest material is capable of emitting fluorescence,
wherein a difference between a singlet excitation energy level and a triplet excitation energy level of the host material is more than 0 eV and less than or equal to 0.2 eV, and
wherein the triplet excitation energy level of the host material is higher than a triplet excitation energy level of the guest material.

2. The light-emitting element according to claim 1 , wherein the singlet excitation energy level of the host material is higher than a singlet excitation energy level of the guest material.

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

4. The light-emitting element according to claim 1 ,
wherein the host material is capable of exhibiting thermally activated delayed fluorescence at room temperature, and
wherein a thermally activated delayed fluorescence emission energy of the host material is higher than a phosphorescence emission energy of the guest material.

5. The light-emitting element according to claim 1 ,
wherein the host material is a first organic compound, and
wherein the guest material is a second organic compound.

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

7. The light-emitting element according to claim 1 , wherein the electroluminescence layer comprises at least one selected from a hole-injection layer, a hole-transport layer, an electron-transport layer, and an electron-injection layer.

8. A display device comprising:
the light-emitting element according to claim 1 ; and
a color filter overlapping with the light-emitting element.

9. An electronic device comprising:
the display device according to claim 8 ; and
a housing or a touch sensor.

10. A lighting device comprising:
the light-emitting element according to claim 1 ; and
a housing or a touch sensor.

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 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 a difference between a singlet excitation energy level and a triplet excitation energy level in the exciplex is more than 0 eV and less than or equal to 0.2 eV, and
wherein the triplet excitation energy level of the exciplex is higher than a triplet excitation energy level of the third organic compound.

12. The light-emitting element according to claim 11 , wherein the singlet excitation energy level of the exciplex is higher than a singlet excitation energy level of the third organic compound.

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

14. The light-emitting element according to claim 11 ,
wherein the exciplex is capable of exhibiting thermally activated delayed fluorescence at room temperature, and
wherein a thermally activated delayed fluorescence emission energy of the exciplex is higher than a phosphorescence emission energy of the third organic compound.

15. 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.

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

17. 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.

18. The light-emitting element according to claim 11 , wherein the electroluminescence layer further comprises one selected from a hole-injection layer, a hole-transport layer, an electron-transport layer, and an electron-injection layer.

19. A display device comprising:
the light-emitting element according to claim 11 ; and
a color filter.

20. An electronic device comprising:
the display device according to claim 19 ; and
a housing or a touch sensor.

21. A lighting device comprising:
the light-emitting element according to claim 11 ; and
a housing or a touch sensor.

22. 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,
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 a difference between a singlet excitation energy level and a triplet excitation energy level in the exciplex is more than 0 eV and less than or equal to 0.2 eV, and
wherein the triplet excitation energy level of the exciplex is higher than a triplet excitation energy level of the third organic compound.

23. The light-emitting element according to claim 22 , wherein the singlet excitation energy level of the exciplex is higher than a singlet excitation energy level of the third organic compound.

24. The light-emitting element according to claim 22 , wherein a difference between the lowest singlet excitation energy level and the lowest triplet excitation energy level in the exciplex is more than 0 eV and less than or equal to 0.2 eV.

25. The light-emitting element according to claim 22 ,
wherein the exciplex is capable of exhibiting thermally activated delayed fluorescence at room temperature, and
wherein a thermally activated delayed fluorescence emission energy of the exciplex is higher than a phosphorescence emission energy of the third organic compound.

26. The light-emitting element according to claim 22 , 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.

27. The light-emitting element according to claim 22 , wh

Assignees

• Semiconductor Energy Lab

Inventors

• Seo Satoshi
• Ohsawa Nobuharu
• Hosoumi Shunsuke
• Ishisone Takahiro

Classifications

• H01L51/5012

  Electricity · mapped topic

• H01L51/5016 Primary

  Electricity · mapped topic

• H01L2251/552

  Electricity · mapped topic

• H10K85/633

  comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom · CPC title

• H10K2101/10

  Triplet emission · CPC title