Light-emitting element, display device, electronic device, and lighting device
A light-emitting element containing a fluorescent material and having high emission efficiency is provided. The light-emitting element contains the fluorescent material and a host material. The host material contains a first organic compound and a second organic compound. The first organic compound and the second organic compound can form an exciplex. The minimum value of a distance between centroids of the fluorescent material and at least one of the first organic compound and the second organic compound is 0.7 nm or more and 5 nm or less.
1. A light-emitting element comprising:
a pair of electrodes; and
a light-emitting layer between the pair of electrodes,
wherein the light-emitting layer comprises:
a fluorescent material as a guest material; and
a first organic compound and a second organic compound capable of forming an exciplex as a host material, and
wherein a minimum value of a distance between a centroid of the fluorescent material and a centroid of the first organic compound or the second organic compound is larger than or equal to 0.7 nm and smaller than or equal to 5 nm;
wherein the minimum value of the distance between the centroids is a distance at the time when a running coordination number calculated by a classical molecular dynamics method exceeds 0.
2. The light-emitting element according to claim 1 , wherein the minimum value of the distance between the centroids corresponds to a distance between the centroid of the fluorescent material and the centroid of the first organic compound or the second organic compound nearest to the fluorescent material.
3. The light-emitting element according to claim 1 , wherein a minimum value of a distance between the centroid of the fluorescent material and a centroid of the first organic compound and a minimum value of a distance between the centroid of the fluorescent material and a centroid of the second organic compound are each larger than or equal to 0.7 nm and smaller than or equal to 5 nm.
4. The light-emitting element according to claim 1 , wherein the fluorescent material comprises at least two alkyl groups each having 2 or more carbon atoms.
5. The light-emitting element according to claim 1 , wherein the fluorescent material comprises at least two branched alkyl groups each having 3 to 10 carbon atoms.
6. The light-emitting element according to claim 1 , wherein the fluorescent material comprises at least two cyclic hydrocarbon groups each having 3 to 10 carbon atoms or at least two bridged cyclic hydrocarbon groups each having 3 to 10 carbon atoms.
7. The light-emitting element according to claim 1 , wherein the fluorescent material comprises condensed aromatic hydrocarbon having 3 to 12 carbon atoms.
8. The light-emitting element according to claim 1 , wherein light emitted from the exciplex has a region overlapping with an absorption band of the fluorescent material on the lowest energy side.
9. The light-emitting element according to claim 1 ,
wherein a proportion of a delayed fluorescence component in light emitted from the exciplex is higher than or equal to 10%, and
wherein the delayed fluorescence component contains a delayed fluorescence component whose fluorescence lifetime is 10 ns or longer and 50 μs or shorter.
10. The light-emitting element according to claim 1 ,
wherein one of the first organic compound and the second organic compound has a function of transporting electrons, and
wherein the other of the first organic compound and the second organic compound has a function of transporting holes.
11. The light-emitting element according to claim 1 ,
wherein one of the first organic compound and the second organic compound comprises a π-electron deficient heteroaromatic ring skeleton, and
wherein the other of the first organic compound and the second organic compound comprises a π-electron rich heteroaromatic ring skeleton or an aromatic amine skeleton.
12. A display device comprising:
the light-emitting element according to claim 1 ; and
at least one of a color filter and a transistor.
13. An electronic device comprising:
the display device according to claim 12 ; and
at least one of a housing and a touch sensor.
14. A lighting device comprising:
the light-emitting element according to claim 1 ; and
at least one of a housing and a touch sensor.
15. A light-emitting element comprising:
a pair of electrodes; and
a light-emitting layer between the pair of electrodes, wherein the light-emitting layer comprises:
a fluorescent material as a guest material; and
a first organic compound and a second organic compound capable of forming an exciplex as a host material,
wherein the fluorescent material has a fluorescence quantum yield of 70% or higher, and wherein a minimum value of a distance between a centroid of the fluorescent material and a centroid of the first organic compound or the second organic compound is larger than or equal to 0.7 nm and smaller than or equal to 5 nm;
wherein the minimum value of the distance between the centroids is a distance at the time when a running coordination number calculated by a classical molecular dynamics method exceeds 0.
16. The light-emitting element according to claim 15 , wherein the minimum value of the distance between the centroids corresponds to a distance between the centroid of the fluorescent material and the centroid of the first organic compound or the second organic compound nearest to the fluorescent material.
17. The light-emitting element according to claim 15 , wherein a minimum value of a distance between the centroid of the fluorescent material and a centroid of the first organic compound and a minimum value of a distance between the centroid of the fluorescent material and a centroid of the second organic compound are each larger than or equal to 0.7 nm and smaller than or equal to 5 nm.
18. The light-emitting element according to claim 15 , wherein the fluorescent material comprises at least two alkyl groups each having 2 or more carbon atoms.
19. The light-emitting element according to claim 15 , wherein the fluorescent material comprises at least two branched alkyl groups each having 3 to 10 carbon atoms.
20. The light-emitting element according to claim 15 , wherein the fluorescent material comprises at least two cyclic hydrocarbon groups each having 3 to 10 carbon atoms or at least two bridged cyclic hydrocarbon groups each having 3 to 10 carbon atoms.
21. The light-emitting element according to claim 15 , wherein the fluorescent material comprises condensed aromatic hydrocarbon having 3 to 12 carbon atoms.
22. The light-emitting element according to claim 15 , wherein light emitted from the exciplex has a region overlapping with an absorption band of the fluorescent material on the lowest energy side.
23. The light-emitting element according to claim 15 ,
wherein a proportion of a delayed fluorescence component in light emitted from the exciplex is higher than or equal to 10%, and
wherein the delayed fluorescence component contains a delayed fluorescence component whose fluorescence lifetime is 10 ns or longer and 50 μs or shorter.
24. The light-emitting element according to claim 15 ,
wherein one of the first organic compound and the second organic compound has a function of transporting electrons, and
wherein the other of the first organic compound and the second organic compound has a function of transporting holes.
25. The light-emitting element according to claim 15 ,
wherein one of the first organic compound and the second organic compound comprises a π-electron deficient heteroaromatic ring skeleton, and
wherein the other of the first organic compound and the second organic compound comprises a π-electron rich heteroaromatic ring skeleton or an aromatic amine skeleton.
26. A display device comprising:
the light-emitting element according to claim 15 ; and
at least one of a color filter and a transistor.
27. An electronic device comprising:
the display device according to claim 26 ; and
at least one of a housing and a touch sensor.
28. A lighting device comprising:
the light-emitting element according to claim 15 ; and
at least one of a housing and a touch sensor.