Light-Emitting Element, Display Device, Electronic Device, and Lighting Device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsNobuharu Ohsawa, Satoshi SEO
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Abstract
A light-emitting element including a fluorescent material as a light-emitting material and having high emission efficiency is provided. The light-emitting element includes a pair of electrodes and an EL layer provided between the pair of electrodes. The EL layer includes a host material and a guest material. The host material is capable of exhibiting thermally activated delayed fluorescence at room temperature. The guest material is capable of exhibiting fluorescence. The second triplet excitation energy level of the guest material is higher than or equal to the lowest singlet excitation energy level of the guest material.
Claims32
A light-emitting element comprising:
- a pair of electrodes;
- and
- an EL layer provided between the pair of electrodes,
- wherein the EL layer comprises a first host material and a guest material,
- wherein the first host material is capable of exhibiting thermally activated delayed fluorescence at room temperature,
- wherein the guest material is capable of exhibiting fluorescence, and
- wherein a second triplet excitation energy level of the guest material is higher than or equal to a lowest singlet excitation energy level of the guest material.
A light-emitting element comprising:
- a pair of electrodes;
- and
- an EL layer provided between the pair of electrodes,
- wherein the EL layer comprises a host material and a guest material,
- wherein the host material is capable of exhibiting thermally activated delayed fluorescence at room temperature,
- wherein the guest material is capable of exhibiting fluorescence,
- wherein a second triplet excitation energy level of the guest material is higher than or equal to a lowest triplet excitation energy level of the host material, and
- wherein the lowest triplet excitation energy level of the host material is higher than or equal to a lowest triplet excitation energy level of the guest material.
A light-emitting element comprising:
- a pair of electrodes;
- and
- an EL layer provided between the pair of electrodes,
- wherein the EL layer comprises a host material and a guest material,
- wherein the host material comprises a first organic compound and a second organic compound,
- wherein an exciplex formed by the first organic compound and the second organic compound is capable of exhibiting thermally activated delayed fluorescence at room temperature,
- wherein the guest material is capable of exhibiting fluorescence,
- wherein a second triplet excitation energy level of the guest material is higher than or equal to a lowest triplet excitation energy level of the exciplex, and
- wherein the lowest triplet excitation energy level of the exciplex is higher than or equal to a lowest triplet excitation energy level of the guest material.
Dependencies are inferred from the claim text.