Light-emitting element, display device, electronic device, and lighting device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsTakahiro Ishisone, Shunsuke Hosoumi, Tatsuyoshi Takahashi, Satoshi Seo
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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.
Claims8
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.
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.
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.
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.
Dependencies are inferred from the claim text.