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

Patent metadata

Field	Value
Publication number	US-11895908-B2
Application number	US-202217713931-A
Country	US
Kind code	B2
Filing date	Apr 5, 2022
Priority date	Mar 9, 2015
Publication date	Feb 6, 2024
Grant date	Feb 6, 2024

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 proportion of a delayed fluorescence component in light emitted from the exciplex is higher than or equal to 5%, and the delayed fluorescence component contains a delayed fluorescence component whose fluorescence lifetime is 10 ns or longer and 50 μs or shorter.

First claim

What is claimed is:

1. A light-emitting element comprising:
a light-emitting layer comprising:
a first substance;
a second substance; and
a third substance,

wherein the third substance is a fluorescent compound,
wherein emission of a mixture of the first substance and the second substance includes a delayed fluorescence component at room temperature,
wherein a peak of the emission of the mixture overlaps with an absorption band on a lowest energy side of the third substance,
wherein a highest occupied molecular orbital level of the first substance is higher than a highest occupied molecular orbital level of the second substance,
wherein a lowest unoccupied molecular orbital level of the first substance is higher than a lowest unoccupied molecular orbital level of the second substance, and
wherein a lifetime of the delayed fluorescence component is 10 ns or longer and 50 μs or shorter.

2. The light-emitting element according to claim 1 , wherein a fluorescence quantum yield of the third substance is 50% or more.

3. The light-emitting element according to 1,
wherein a highest occupied molecular orbital level of the first substance is higher than a highest occupied molecular orbital level of the second substance by 0.1 eV or more, and
wherein a lowest unoccupied molecular orbital level of the first substance is higher than a lowest unoccupied molecular orbital level of the second substance by 0.1 eV or more.

4. The light-emitting element according to claim 1 , wherein a weight ratio of the third substance in the light-emitting layer is equal to or greater than 0.001 and lower than or equal to 0.05.

5. A light-emitting element comprising:
a light-emitting layer comprising:
a first substance;
a second substance; and
a third substance,

wherein the third substance is a fluorescent compound,
wherein emission of a mixture of the first substance and the second substance includes a delayed fluorescence component at room temperature,
wherein a peak of the delayed fluorescence component overlaps with an absorption band on a lowest energy side of the third substance,
wherein a highest occupied molecular orbital level of the first substance is higher than a highest occupied molecular orbital level of the second substance,
wherein a lowest unoccupied molecular orbital level of the first substance is higher than a lowest unoccupied molecular orbital level of the second substance, and
wherein a lifetime of the delayed fluorescence component is 10 ns or longer and 50 μs or shorter.

6. The light-emitting element according to claim 5 , wherein a fluorescence quantum yield of the third substance is 50% or more.

7. The light-emitting element according to 5,
wherein a highest occupied molecular orbital level of the first substance is higher than a highest occupied molecular orbital level of the second substance by 0.1 eV or more, and
wherein a lowest unoccupied molecular orbital level of the first substance is higher than a lowest unoccupied molecular orbital level of the second substance by 0.1 eV or more.

8. The light-emitting element according to claim 5 , wherein a weight ratio of the third substance in the light-emitting layer is equal to or greater than 0.001 and lower than or equal to 0.05.

Assignees

• Semiconductor Energy Lab

Inventors

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

Classifications

• H10K2101/30

  Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values · CPC title

• H10K2101/20

  Delayed fluorescence emission · CPC title

• H10K85/611 Primary

  Charge transfer complexes · CPC title

• H10K50/11 Primary

  characterised by the electroluminescent [EL] layers · CPC title

• H10K50/19

  Tandem OLEDs · CPC title