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

Patent metadata

Field	Value
Publication number	US-11038134-B2
Application number	US-201916595639-A
Country	US
Kind code	B2
Filing date	Oct 8, 2019
Priority date	Mar 9, 2015
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

A light-emitting element containing a fluorescent material and having high emission efficiency is provided. The light-emitting element contains the fluorescent material and a host material. The host material contains a first organic compound and a second organic compound. The first organic compound and the second organic compound can form an exciplex. The minimum value of a distance between centroids of the fluorescent material and at least one of the first organic compound and the second organic compound is 0.7 nm or more and 5 nm or less.

First claim

What is claimed is:

1. A light-emitting device comprising:
a pair of electrodes over a substrate; and
a light-emitting layer between the pair of electrodes,
wherein the light-emitting layer comprises:
a fluorescent material as a guest material; and
a first organic compound and a second organic compound capable of forming an exciplex as a host material,

wherein the fluorescent material comprises at least two substituents and condensed aromatic hydrocarbon having at least three rings,
wherein the two substituents comprise any one of branched alkyl groups each having 3 to 10 carbon atoms, cyclic hydrocarbon groups each having 3 to 10 carbon atoms, bridged cyclic hydrocarbon groups each having 3 to 10 carbon atoms,
wherein light emitted from the exciplex has a region overlapping with an absorption band of the fluorescent material on the lowest energy side,
wherein the first organic compound comprises a benzofuro[3,2-d]pyrimidine skeleton, and
wherein the second organic compound comprises a carbazole skeleton.

2. The light-emitting device according to claim 1 ,
wherein a proportion of a delayed fluorescence component in light emitted from the exciplex is higher than or equal to 10%, and
wherein the delayed fluorescence component contains a delayed fluorescence component whose fluorescence lifetime is 10 ns or longer and 50 μs or shorter.

3. The light-emitting device according to claim 1 ,
wherein one of the first organic compound and the second organic compound has a function of transporting electrons, and
wherein the other of the first organic compound and the second organic compound has a function of transporting holes.

4. The light-emitting device according to claim 1 ,
wherein one of the first organic compound and the second organic compound comprises a π-electron deficient heteroaromatic ring skeleton, and
wherein the other of the first organic compound and the second organic compound comprises a π-electron rich heteroaromatic ring skeleton or an aromatic amine skeleton.

5. The light-emitting device according to claim 1 ,
wherein a minimum value of a distance between a centroid of the fluorescent material and a centroid of the first organic compound or the second organic compound is larger than or equal to 0.7 nm and smaller than or equal to 5 nm, and
wherein the minimum value of the distance between the centroids is a distance at the time when a running coordination number calculated by a classical molecular dynamics method exceeds 0.

6. The light-emitting device according to claim 5 , wherein the minimum value of the distance between the centroids corresponds to a distance between the centroid of the fluorescent material and the centroid of the first organic compound or the second organic compound nearest to the fluorescent material.

7. The light-emitting device according to claim 5 , wherein a minimum value of a distance between the centroid of the fluorescent material and a centroid of the first organic compound and a minimum value of a distance between the centroid of the fluorescent material and a centroid of the second organic compound are each larger than or equal to 0.7 nm and smaller than or equal to 5 nm.

8. The light-emitting device according to claim 1 , wherein the condensed aromatic hydrocarbon is one selected from the group consisting of an anthracene skeleton, a phenanthren skeleton, a fluorine skeleton, an indacene skeleton, a tetracene skeleton, a triphenylen skeleton, a chrysene skeleton, a pyrene skeleton, a fluoranthene skeleton, a pentacene skeleton, a perylene skeleton, a rubicene skeleton, a trinaphthylene skeleton, and a dibenzoperiflanthene skeleton.

9. The light-emitting device according to claim 1 , wherein each of the two substituents is a tert-butyl group.

10. A light-emitting device comprising:
a pair of electrodes over a substrate; and
a light-emitting layer between the pair of electrodes,
wherein the light-emitting layer comprises:
a fluorescent material as a guest material; and
a first organic compound and a second organic compound capable of forming an exciplex as a host material,

wherein the fluorescent material has a fluorescence quantum yield of 70% or higher, and
wherein the fluorescent material comprises at least two substituents and condensed aromatic hydrocarbon having at least three rings,
wherein the two substituents comprise any one of branched alkyl groups each having 3 to 10 carbon atoms, cyclic hydrocarbon groups each having 3 to 10 carbon atoms, bridged cyclic hydrocarbon groups each having 3 to 10 carbon atoms,
wherein light emitted from the exciplex has a region overlapping with an absorption band of the fluorescent material on the lowest energy side,
wherein the first organic compound comprises a benzofuro[3,2-d]pyrimidine skeleton, and
wherein the second organic compound comprises a carbazole skeleton.

11. The light-emitting device according to claim 10 ,
wherein a proportion of a delayed fluorescence component in light emitted from the exciplex is higher than or equal to 10%, and
wherein the delayed fluorescence component contains a delayed fluorescence component whose fluorescence lifetime is 10 ns or longer and 50 μs or shorter.

12. The light-emitting device according to claim 10 ,
wherein one of the first organic compound and the second organic compound has a function of transporting electrons, and
wherein the other of the first organic compound and the second organic compound has a function of transporting holes.

13. The light-emitting device according to claim 10 ,
wherein one of the first organic compound and the second organic compound comprises a π-electron deficient heteroaromatic ring skeleton, and wherein the other of the first organic compound and the second organic compound comprises a π-electron rich heteroaromatic ring skeleton or an aromatic amine skeleton.

14. The light-emitting device according to claim 10 ,
wherein a minimum value of a distance between a centroid of the fluorescent material and a centroid of the first organic compound or the second organic compound is larger than or equal to 0.7 nm and smaller than or equal to 5 nm, and
wherein the minimum value of the distance between the centroids is a distance at the time when a running coordination number calculated by a classical molecular dynamics method exceeds 0.

15. The light-emitting device according to claim 14 , wherein the minimum value of the distance between the centroids corresponds to a distance between the centroid of the fluorescent material and the centroid of the first organic compound or the second organic compound nearest to the fluorescent material.

16. The light-emitting device according to claim 14 , wherein a minimum value of a distance between the centroid of the fluorescent material and a centroid of the first organic compound and a minimum value of a distance between the centroid of the fluorescent material and a centroid of the second organic compound are each larger than or equal to 0.7 nm and smaller than or equal to 5 nm.

17. The light-emitting device according to claim 10 , wherein the condensed aromatic hydrocarbon is one selected from the group consisting of an anthracene skeleton, a phenanthren skeleton, a fluorine skeleton, an indacene skeleton, a tetracene skeleton, a triphenylen skeleton, a chrysene skeleton, a pyrene skeleton, a fluoranthene skeleton, a pentacene skeleton, a perylene skeleton, a rubicene skeleton, a trinaphthylene skeleton, and a dibenzoperiflanthene skeleton.

18. The light-emitting device according to claim 10 , wherein e

Assignees

• Semiconductor Energy Lab

Inventors

• Hosoumi Shunsuke
• Ishisone Takahiro
• Takahashi Tatsuyoshi
• Seo Satoshi

Classifications

• H10K59/1213

  the pixel elements being TFTs · CPC title

• H10K59/38

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

• H10K85/649

  Aromatic compounds comprising a hetero atom · CPC title

• H10K50/11 Primary

  characterised by the electroluminescent [EL] layers · CPC title

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title