Light-emitting element with fluorescent material, display device, electronic device, and lighting device

Patent metadata

Field	Value
Publication number	US-11997861-B2
Application number	US-202318100054-A
Country	US
Kind code	B2
Filing date	Jan 23, 2023
Priority date	Aug 29, 2014
Publication date	May 28, 2024
Grant date	May 28, 2024

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 device comprising:
a first electrode;
a light-emitting layer over the first electrode, the light-emitting layer comprising:
a first compound capable of exhibiting thermally activated delayed fluorescence at room temperature, and
a second compound; and
a light-emitting material capable of exhibiting fluorescence,

a second electrode over the light-emitting layer,
wherein the first compound comprises a condensed heterocyclic ring having three six-membered rings,
wherein the light-emitting material comprises an anthracene ring,
wherein a triplet excitation energy level of the first compound is higher than a triplet excitation energy level of the light-emitting material,
wherein a singlet excitation energy level of the first compound is higher than a singlet excitation energy level of the light-emitting material,
wherein an emission spectrum of the first compound comprises a region overlapping with an absorption band having a longest wavelength in an absorption spectrum of the light-emitting material, and
wherein light emitted from the light-emitting layer comprises light emitted from the light-emitting material.

2. The light-emitting device according to claim 1 , wherein the light emitted from the light-emitting layer further comprises light emitted from the first compound.

3. The light-emitting device according to claim 1 , wherein the condensed heterocyclic ring comprises nitrogen.

4. The light-emitting device according to claim 1 , wherein the condensed heterocyclic ring comprises oxygen.

5. The light-emitting device according to claim 1 , further comprising a charge-generation layer over the light-emitting layer, and a first light-emitting unit over the charge-generation layer,
wherein the light-emitting layer is included in a second light-emitting unit.

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

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

8. A light-emitting device comprising:
a first electrode;
a first light-emitting layer over the first electrode, the light-emitting layer comprising:
a first compound capable of exhibiting thermally activated delayed fluorescence at room temperature, and
a second compound; and
a light-emitting material capable of exhibiting fluorescence,

a second electrode over the first light-emitting layer,
wherein the first compound comprises an acridine skeleton,
wherein the light-emitting material comprises an anthracene ring,
wherein a triplet excitation energy level of the first compound is higher than a triplet excitation energy level of the light-emitting material,
wherein a singlet excitation energy level of the first compound is higher than a singlet excitation energy level of the light-emitting material,
wherein an emission spectrum of the first compound comprises a region overlapping with an absorption band having a longest wavelength in an absorption spectrum of the light-emitting material, and
wherein light emitted from the first light-emitting layer comprises light emitted from the light-emitting material.

9. The light-emitting device according to claim 8 , wherein a difference between the singlet excitation energy level and the triplet excitation energy level of the first compound is more than 0 eV and less than or equal to 0.2 eV.

10. The light-emitting device according to claim 8 ,
wherein the light-emitting device comprises a first light-emitting unit comprising the first light-emitting layer, a charge-generation layer over the first light-emitting unit, and a second light-emitting unit comprising a second light-emitting layer.

11. The light-emitting device according to claim 10 , wherein the second light-emitting layer has a same structure as the first light-emitting layer.

12. The light-emitting device according to claim 8 , wherein the light emitted from the first light-emitting layer further comprises light emitted from the first compound.

13. An electronic device comprising the light-emitting device according to claim 8 .

14. A light-emitting device comprising:
a first electrode;
a light-emitting layer over the first electrode, the light-emitting layer comprising:
a first compound capable of exhibiting thermally activated delayed fluorescence at room temperature, and
a second compound; and
a light-emitting material capable of exhibiting fluorescence,

a second electrode over the light-emitting layer,
wherein the first compound comprises a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring,
wherein the light-emitting material comprises an anthracene ring,
wherein a triplet excitation energy level of the first compound is higher than a triplet excitation energy level of the light-emitting material,
wherein a singlet excitation energy level of the first compound is higher than a singlet excitation energy level of the light-emitting material,
wherein an emission spectrum of the first compound comprises a region overlapping with an absorption band having a longest wavelength in an absorption spectrum of the light-emitting material, and
wherein light emitted from the light-emitting layer comprises light emitted from the light-emitting material.

15. The light-emitting device according to claim 14 , wherein the π-electron deficient heteroaromatic ring is a triazine ring or a triazole ring.

16. The light-emitting device according to claim 14 , wherein the light emitted from the light-emitting layer further comprises light emitted from the first compound.

17. The light-emitting device according to claim 14 , wherein the π-electron rich heteroaromatic ring and the π-electron deficient heteroaromatic ring are directly bonded to each other.

18. The light-emitting device according to claim 14 , wherein a difference between the singlet excitation energy level and the triplet excitation energy level of the first compound is more than 0 eV and less than or equal to 0.2 eV.

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

Assignees

• Semiconductor Energy Lab

Inventors

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

Classifications

• H10K85/633

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

• H10K50/82

  Cathodes · CPC title

• H10K59/38

  comprising colour filters or colour changing media [CCM] · CPC title

• H10K50/19

  Tandem OLEDs · CPC title

• H10K50/81

  Anodes · CPC title