Light-emitting element, display device, electronic device, and lighting device each including TADF organic compound
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsNobuharu Ohsawa, Satoshi Seo
Life of this patent
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Abstract
A light-emitting element having high emission efficiency is provided. The light-emitting element includes a first organic compound, a second organic compound, and a third organic compound. The first organic compound has a function of converting triplet excitation energy into light emission. The second organic compound is preferably a TADF material. The third organic compound is a fluorescent compound. Light emitted from the light-emitting element is obtained from the third organic compound. Triplet excitation energy in a light-emitting layer is transferred to the third organic compound by reverse intersystem crossing caused by the second organic compound or through the first organic compound.
Claims27
A light-emitting device comprising:
- a first electrode;
- a light-emitting layer over the first electrode, the light-emitting layer comprising:
- a first organic compound configured to convert triplet excitation energy into light emission;
- a second organic compound;
- and
- a third organic compound configured to convert singlet excitation energy into light emission;
- and
- a second electrode over the light-emitting layer,
- wherein a difference between the lowest singlet excitation energy level of the second organic compound and the lowest triplet excitation energy level of the second organic compound is greater than or equal to 0 eV and less than or equal to 0.2 eV,
- wherein light emission from the light-emitting layer comprises light emission from the third organic compound, and
- wherein the lowest triplet excitation energy level of the first organic compound is higher than or equal to the lowest triplet excitation energy of the third organic compound.
A light-emitting device comprising:
- a first electrode;
- a light-emitting layer over the first electrode, the light-emitting layer comprising:
- a first organic compound configured to convert triplet excitation energy into light emission;
- a second organic compound comprising a 7c-electron rich skeleton and a 7C-electron deficient skeleton;
- and
- a third organic compound configured to convert singlet excitation energy into light emission;
- and
- a second electrode over the light-emitting layer,
- wherein light emission from the light-emitting layer comprises light emission from the third organic compound, and
- wherein the lowest triplet excitation energy level of the first organic compound is higher than or equal to the lowest triplet excitation energy of the third organic compound.
Dependencies are inferred from the claim text.