Light-emitting element
Provided is a light-emitting element with high external quantum efficiency and a low drive voltage. The light-emitting element includes a light-emitting layer which contains a phosphorescent compound and a material exhibiting thermally activated delayed fluorescence between a pair of electrodes, wherein a peak of a fluorescence spectrum and/or a peak of a phosphorescence spectrum of the material exhibiting thermally activated delayed fluorescence overlap(s) with a lowest-energy-side absorption band in an absorption spectrum of the phosphorescent compound, and wherein the phosphorescent compound exhibits phosphorescence in the light-emitting layer by voltage application between the pair of electrodes.
1. A light-emitting element comprising:
a first electrode and a second electrode;
a light-emitting layer between the first electrode and the second electrode;
a hole-transport layer between the light-emitting layer and the first electrode; and
an electron-transport layer between the light-emitting layer and the second electrode,
wherein the light-emitting layer comprises a phosphorescent compound and a thermally activated delayed fluorescence material.
2. The light-emitting element according to claim 1 , wherein in the light-emitting layer, the phosphorescent compound functions as guest and the thermally activated delayed fluorescence material functions as host.
3. The light-emitting element according to claim 1 , wherein at least one of a peak of a fluorescence spectrum and a peak of a phosphorescence spectrum of the thermally activated delayed fluorescence material overlaps with a lowest-energy-side absorption band in an absorption spectrum of the phosphorescent compound.
4. The light-emitting element according to claim 1 , wherein the phosphorescent compound is an organometallic complex.
5. A light-emitting device comprising the light-emitting element according to claim 1 .
6. A light-emitting element comprising:
a first electrode and a second electrode;
a light-emitting layer between the first electrode and the second electrode;
a first layer between the light-emitting layer and the second electrode;
a second layer between the first layer and the second electrode; and
a third layer between the second layer and the second electrode,
wherein the first layer includes a first material with an electron-injection property,
wherein the second layer includes a second material with an electron-transport property,
wherein the third layer includes a third material with a hole-transport property and an acceptor material, and
wherein the light-emitting layer comprises a phosphorescent compound and a thermally activated delayed fluorescence material.
7. The light-emitting element according to claim 6 , wherein in the light-emitting layer, the phosphorescent compound functions as guest and the thermally activated delayed fluorescence material functions as host.
8. The light-emitting element according to claim 6 , wherein at least one of a peak of a fluorescence spectrum and a peak of a phosphorescence spectrum of the thermally activated delayed fluorescence material overlaps with a lowest-energy-side absorption band in an absorption spectrum of the phosphorescent compound.
9. The light-emitting element according to claim 6 , wherein the phosphorescent compound is an organometallic complex.
10. A light-emitting device comprising the light-emitting element according to claim 6 .
11. A light-emitting element comprising:
a first electrode and a second electrode;
a first light-emitting layer and a second light-emitting layer between the first electrode and the second electrode; and
an intermediate layer between the first light-emitting layer and the second light-emitting layer,
wherein the first light-emitting layer comprises a first phosphorescent compound and a first thermally activated delayed fluorescence material, and
wherein the second light-emitting layer comprises a second phosphorescent compound and a second thermally activated delayed fluorescence material.
12. The light-emitting element according to claim 11 , wherein in the first light-emitting layer, the first phosphorescent compound functions as guest and the first thermally activated delayed fluorescence material functions as host.
13. The light-emitting element according to claim 11 , wherein in the second light-emitting layer, the second phosphorescent compound functions as guest and the second thermally activated delayed fluorescence material functions as host.
14. The light-emitting element according to claim 11 , wherein at least one of a peak of a fluorescence spectrum and a peak of a phosphorescence spectrum of the first thermally activated delayed fluorescence material overlaps with a lowest-energy-side absorption band in an absorption spectrum of the first phosphorescent compound.
15. The light-emitting element according to claim 11 , wherein at least one of a peak of a fluorescence spectrum and a peak of a phosphorescence spectrum of the second thermally activated delayed fluorescence material overlaps with a lowest-energy-side absorption band in an absorption spectrum of the second phosphorescent compound.
16. The light-emitting element according to claim 11 , wherein the first phosphorescent compound is an organometallic complex.
17. The light-emitting element according to claim 11 , wherein the second phosphorescent compound is an organometallic complex.
18. A light-emitting device comprising the light-emitting element according to claim 11 .