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 comprises a light-emitting layer,
wherein the light-emitting layer comprises a first organic compound, a second organic compound, and a light-emitting substance converting triplet excitation energy into light emission,
wherein a combination of the first organic compound and the second organic compound forms an exciplex,
wherein the first organic compound comprises a 6-membered nitrogen-containing heteroaromatic ring and a carbazole skeleton,
wherein the 6-membered nitrogen-containing heteroaromatic ring is pyrazine, pyridazine, triazine, or tetrazine,
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 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 0.3 eV.
3. A light-emitting device comprising the light-emitting element according to claim 1 .
4. An electronic device comprising:
the light-emitting device according to claim 3 ; and
a connection terminal or an operation key.
5. A lighting device comprising:
the light-emitting device according to claim 3 ; and
a housing.
6. A light-emitting element comprising:
an EL layer between an anode and a cathode,
wherein the EL layer comprises a light-emitting layer,
wherein the light-emitting layer comprises a first organic compound, a second organic compound, and a light-emitting substance converting triplet excitation energy into light emission,
wherein a combination of the first organic compound and the second organic compound forms an exciplex,
wherein the first organic compound comprises a 6-membered nitrogen-containing heteroaromatic ring and a carbazole skeleton,
wherein a HOMO level of the first organic compound is lower than a HOMO level of the second organic compound,
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, and
wherein a benzene ring is condensed with the 6-membered nitrogen-containing heteroaromatic ring.
7. The light-emitting element according to claim 6 , 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 0.3 eV.
8. The light-emitting element according to claim 6 , wherein the 6-membered nitrogen-containing heteroaromatic ring is pyridine, pyrazine, pyrimidine, pyridazine, triazine, or tetrazine.
9. The light-emitting element according to claim 6 , wherein the 6-membered nitrogen-containing heteroaromatic ring condensed with the benzene ring is quinoline, isoquinoline, dibenzo[f,h]quinolone, naphthyridine, dibenzo[f,h]quinoxaline or dibenzo[f,h]quinazoline.
10. A light-emitting device comprising the light-emitting element according to claim 6 .
11. An electronic device comprising:
the light-emitting device according to claim 10 ; and
a connection terminal or an operation key.
12. Alighting device comprising:
the light-emitting device according to claim 11 ; and
a housing.