Light-emitting element, display device, electronic device, and lighting device
A light-emitting element containing a light-emitting material and having high light emission efficiency is provided. The light-emitting element includes a host material and a guest material. The host material includes at least a first molecule and a second molecule having the same molecular structure. The guest material has a function of exhibiting fluorescence or converting triplet excitation energy into light emission. The first molecule and the second molecule each include a first skeleton, a second skeleton, and a third skeleton, and the first skeleton and the second skeleton are bonded to each other through the third skeleton. The first skeleton includes at least one of a π-electron rich heteroaromatic skeleton and an aromatic amine skeleton and the second skeleton includes a π-electron deficient heteroaromatic skeleton. The first molecule and the second molecule have a function of forming an excited complex.
1. A light-emitting device comprising:
a light-emitting layer, the light-emitting layer comprising:
a host material comprising at least a first molecule and a second molecule, the first molecule and the second molecule having the same molecular structure; and
a phosphorescent material as a guest material,
wherein each of the first molecule and the second molecule comprises:
a first skeleton comprising at least one of a π-electron rich heteroaromatic skeleton and an aromatic amine skeleton;
a second skeleton comprising a π-electron deficient heteroaromatic skeleton which is not a benzofuropyrimidine skeleton; and
a third skeleton,
wherein the first skeleton and the second skeleton are bonded to each other through the third skeleton, and
wherein the first molecule and the second molecule are configured to form an excited complex with the first skeleton in the first molecule and the second skeleton in the second molecule.
2. The light-emitting device according to claim 1 , wherein the π-electron deficient heteroaromatic skeleton comprises at least one of a pyridine skeleton, a diazine skeleton, and a triazine skeleton.
3. The light-emitting device according to claim 1 , wherein the π-electron rich heteroaromatic skeleton comprises at least one of a thiophene skeleton, a furan skeleton, and a pyrrole skeleton.
4. The light-emitting device according to claim 1 , wherein the third skeleton comprises at least one of a m-phenylene group and an o-phenylene group.
5. The light-emitting device according to claim 1 , wherein the third skeleton has a structure where an arylene group and at least one of a m-phenylene group and an o-phenylene group are bonded to each other.
6. The light-emitting device according to claim 1 , wherein the third skeleton comprises a biphenyldiyl group.
7. The light-emitting device according to claim 1 , wherein the excited complex is configured to exhibit thermally activated delayed fluorescence at room temperature.
8. The light-emitting device according to claim 1 , wherein the excited complex is configured to supply excitation energy to the phosphorescent material.
9. The light-emitting device according to claim 1 , wherein light emitted from the excited complex overlaps with an absorption band of the phosphorescent material on the lowest energy side.
10. A light-emitting device comprising:
a light-emitting layer, the light-emitting layer comprising:
a host material comprising a compound comprising at least a first molecule and a second molecule, the first molecule and the second molecule having the same molecular structure; and
a phosphorescent material as a guest material,
wherein each of the first molecule and the second molecule comprises:
a first skeleton comprising at least one of a π-electron rich heteroaromatic skeleton and an aromatic amine skeleton;
a second skeleton comprising a π-electron deficient heteroaromatic skeleton; and
a third skeleton,
wherein the first skeleton and the second skeleton are bonded to each other through the third skeleton,
wherein the first molecule and the second molecule are configured to form an excited complex with the first skeleton in the first molecule and the second skeleton in the second molecule, and
wherein a difference between a peak of an emission spectrum of the compound in a toluene solution and a peak of an emission spectrum of a thin film of the compound is 30 nm or more.
11. The light-emitting device according to claim 10 , wherein the π-electron deficient heteroaromatic skeleton comprises at least one of a pyridine skeleton, a diazine skeleton, and a triazine skeleton.
12. The light-emitting device according to claim 10 , wherein the third skeleton comprises a biphenyldiyl group.