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

1. A light-emitting element comprising:

a pair of electrodes; and

an EL layer between the pair of electrodes,

wherein the EL layer comprises a light-emitting layer having a first organic compound, a second organic compound, and a guest material,

wherein the first organic compound has a function of emitting a thermally activated delayed fluorescence at room temperature,

wherein the guest material has a function of emitting fluorescence,

wherein a HOMO level of the first organic compound is higher than or equal to a HOMO level of the second organic compound,

wherein a LUMO level of the first organic compound is lower than or equal to a LUMO level of the second organic compound, and

wherein a triplet excitation energy level of the second organic compound is higher than a triplet excitation energy level of the guest material.

2. The light-emitting element according to claim 1 , wherein a difference between a singlet excitation energy level of the first organic compound and a triplet excitation energy level of the first organic compound is larger than 0 eV and smaller than or equal to 0.2 eV.

3. The light-emitting element according to claim 1 , wherein the guest material emits light.

4. The light-emitting element according to claim 1 ,

wherein the first organic compound comprises a first π-electron deficient heteroaromatic skeleton and a first π-electron rich heteroaromatic skeleton, and

wherein the second organic compound comprises a second π-electron deficient heteroaromatic skeleton and a second π-electron rich heteroaromatic skeleton.

5. The light-emitting element according to claim 4 ,

wherein the first π-electron deficient heteroaromatic skeleton comprises a diazine skeleton or a triazine skeleton,

wherein the first π-electron rich heteroaromatic skeleton comprises any one or more of an acridine skeleton, a phenoxazine skeleton, or a 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeleton,

wherein the second π-electron deficient heteroaromatic skeleton comprises a pyridine skeleton or a diazine skeleton, and

wherein the second π-electron rich heteroaromatic skeleton comprises any one or more of a furan skeleton, a thiophene skeleton, a fluorine skeleton, and a pyrrole skeleton.

6. The light-emitting element according to claim 1 ,

wherein a weight ratio of the second organic compound to the first organic compound is from 1:0.05 to 1:0.5, and

wherein a weight ratio of the second organic compound to the guest material is from 1:0.001 to 1:0.01.

7. A display device comprising:

the light-emitting element according to claim 1 ; and

a color filter, a sealant, or a transistor.

8. An electronic device comprising:

the display device according to claim 7 , and

a housing or a function of a touch sensor.

9. A lighting device comprising:

the light-emitting element according to claim 1 , and

a housing or a function of a touch sensor.

10. A light-emitting element comprising:

a pair of electrodes; and

an EL layer between the pair of electrodes,

wherein the EL layer comprises a light-emitting layer having a first organic compound, a second organic compound, and a guest material,

wherein the first organic compound has a function of emitting a thermally activated delayed fluorescence at room temperature,

wherein the guest material has a function of emitting fluorescence,

wherein an oxidation potential of the first organic compound is lower than or equal to an oxidation potential of the second organic compound,

wherein a reduction potential of the first organic compound is higher than or equal to a reduction of the second organic compound, and

wherein a triplet excitation energy level of the second organic compound is higher than a triplet excitation energy level of the guest material.

11. The light-emitting element according to claim 10 , wherein a difference between a singlet excitation energy level of the first organic compound and a triplet excitation energy level of the first organic compound is larger than 0 eV and smaller than or equal to 0.2 eV.

12. The light-emitting element according to claim 10 , wherein the guest material emits light.

13. The light-emitting element according to claim 10 ,

wherein the first organic compound comprises a first π-electron deficient heteroaromatic skeleton and a first π-electron rich heteroaromatic skeleton, and

wherein the second organic compound comprises a second π-electron deficient heteroaromatic skeleton and a second π-electron rich heteroaromatic skeleton.

14. The light-emitting element according to claim 13 ,

wherein the first π-electron deficient heteroaromatic skeleton comprises a diazine skeleton or a triazine skeleton,

wherein the first π-electron rich heteroaromatic skeleton comprises any one or more of an acridine skeleton, a phenoxazine skeleton, or a 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeleton,

wherein the second π-electron deficient heteroaromatic skeleton comprises a pyridine skeleton or a diazine skeleton, and

wherein the second π-electron rich heteroaromatic skeleton comprises any one or more of a furan skeleton, a thiophene skeleton, a fluorine skeleton, and a pyrrole skeleton.

15. The light-emitting element according to claim 10 ,

wherein a weight ratio of the second organic compound to the first organic compound is from 1:0.05 to 1:0.5, and

wherein a weight ratio of the second organic compound to the guest material is from 1:0.001 to 1:0.01.

16. A display device comprising:

the light-emitting element according to claim 10 ; and

a color filter, a sealant, or a transistor.

17. An electronic device comprising:

the display device according to claim 16 , and

a housing or a function of a touch sensor.

18. A lighting device comprising:

the light-emitting element according to claim 10 , and

a housing or a function of a touch sensor.