Light-emitting element, light-emitting device, electronic device, lighting device, and organic compound
To provide a light-emitting element with an improved reliability, a light-emitting element with a high current efficiency (or a high quantum efficiency), and a novel dibenzo[f,h]quinoxaline derivative that is favorably used in a light-emitting element which is one embodiment of the present invention. A light-emitting element includes an EL layer between an anode and a cathode. The EL layer includes a light-emitting layer; the light-emitting layer contains a first organic compound having an electron-transport property and a hole-transport property, a second organic compound having a hole-transport property, and a light-emitting substance; the combination of the first organic compound and the second organic compound forms an exciplex; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; and a difference between the HOMO level of the first organic compound and the HOMO level of the second organic compound is less than or equal to 0.4 eV.
1. A light-emitting element comprising:
an EL layer between an anode and a cathode,
wherein the EL layer includes a light-emitting layer,
wherein the light-emitting layer contains a first organic compound, a second organic compound, and a light-emitting substance,
wherein a combination of the first organic compound and the second organic compound forms an exciplex,
wherein the first organic compound includes a 6-membered nitrogen-containing heteroaromatic ring and a bicarbazole skeleton,
wherein a HOMO level of the first organic compound is lower than a HOMO level of the second organic compound, and
wherein a difference between the HOMO level of the first organic compound and the HOMO level of the second organic compound is less than or equal to 0.4 eV.
2. The light-emitting element according to claim 1 , wherein the bicarbazole skeleton is a 3,3′-bicarbazole skeleton or a 2,3′-bicarbazole skeleton.
3. The light-emitting element according to claim 1 , wherein the light-emitting substance is a phosphorescent compound.
4. The light-emitting element according to claim 1 ,
wherein the EL layer includes a hole-transport layer, the hole-transport layer being in contact with the light-emitting layer and containing a third organic compound, and
wherein a HOMO level of the third organic compound is lower than the HOMO level of the second organic compound.
5. The light-emitting element according to claim 1 ,
wherein the first organic compound is represented by a general formula (G0),
wherein A represents a dibenzo[f,h]quinoxalinyl group; R 1 to R 15 represent independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 5 to 7 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms; and Ar represents a substituted or unsubstituted arylene group having 6 to 25 carbon atoms or a single bond.
6. A light-emitting device comprising:
the light-emitting element according to claim 1 ; and
a housing.
7. An electronic device comprising:
the light-emitting device according to claim 6 ; and
a connection terminal or an operation key.
8. A lighting device comprising:
the light-emitting element according to claim 1 ; and
a housing.
9. A light-emitting element comprising:
an EL layer between an anode and a cathode,
wherein the EL layer includes a light-emitting layer,
wherein the light-emitting layer contains a first organic compound, a second organic compound, and a light-emitting substance,
wherein a combination of the first organic compound and the second organic compound foal's an exciplex,
wherein the first organic compound includes a 6-membered nitrogen-containing heteroaromatic ring and a bicarbazole skeleton and does not contain a triarylamine skeleton,
wherein the second organic compound includes a triarylamine skeleton, and
wherein a difference between a HOMO level of the first organic compound and a HOMO level of the second organic compound is less than or equal to 0.4 eV.
10. The light-emitting element according to claim 9 , wherein the bicarbazole skeleton is a 3,3′-bicarbazole skeleton or a 2,3′-bicarbazole skeleton.
11. The light-emitting element according to claim 9 , wherein the light-emitting substance is a phosphorescent compound.
12. The light-emitting element according to claim 9 ,
wherein the EL layer includes a hole-transport layer, the hole-transport layer being in contact with the light-emitting layer and containing a third organic compound, and
wherein a HOMO level of the third organic compound is lower than the HOMO level of the second organic compound.
13. The light-emitting element according to claim 9 ,
wherein the first organic compound is represented by a general formula (G0),
wherein A represents a dibenzo[f,h]quinoxalinyl group; R 1 to R 15 represent independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 5 to 7 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms; and Ar represents a substituted or unsubstituted arylene group having 6 to 25 carbon atoms or a single bond.
14. A light-emitting device comprising:
the light-emitting element according to claim 9 ; and
a housing.
15. An electronic device comprising:
the light-emitting device according to claim 14 ; and
a connection terminal or an operation key.
16. A lighting device comprising:
the light-emitting element according to claim 9 ; and
a housing.