Light-emitting element, light-emitting device, electronic device, and lighting device
Provided is a novel light-emitting element, a light-emitting element with a long lifetime, or a light-emitting element with high emission efficiency. The light-emitting element includes an EL layer between a pair of electrodes. The EL layer includes at least a light-emitting layer containing a fluorescent substance and a host material, a first electron-transport layer containing a first electron-transport material, and a second electron-transport layer containing a second electron-transport material, which are in contact with each other and in this order. The LUMO level of each of the host material and the second electron-transport material is higher than the LUMO level of the first electron-transport material.
1. A light-emitting element comprising:
an anode;
a cathode; and
an EL layer between the anode and the cathode,
wherein the EL layer comprises a light-emitting layer, a first electron-transport layer, and a second electron-transport layer,
wherein the first electron-transport layer is between the light-emitting layer and the second electron-transport layer,
wherein the light-emitting layer has a region in contact with the first electron-transport layer,
wherein the second electron-transport layer has a region in contact with the first electron-transport layer,
wherein the light-emitting layer comprises a fluorescent substance and a host material,
wherein the first electron-transport layer comprises a first material,
wherein the second electron-transport layer comprises a second material,
wherein the host material is different from the first material and the second material,
wherein a LUMO level of the host material is higher than a LUMO level of the first material,
wherein a LUMO level of the second material is higher than the LUMO level of the first material,
wherein the host material is a substance including a condensed aromatic ring skeleton including 3 to 6 rings,
wherein the first material is a substance including a first heteroaromatic ring skeleton,
wherein the second material is a substance including a second heteroaromatic ring skeleton, and
wherein the substance including the first heteroaromatic ring skeleton is different from the substance including the second heteroaromatic ring skeleton.
2. The light-emitting element according to claim 1 ,
wherein each of the substance including the first heteroaromatic ring skeleton and the substance including the second heteroaromatic ring skeleton is a substance including a six-membered nitrogen-containing heteroaromatic ring skeleton.
3. The light-emitting element according to claim 1 ,
wherein the substance including the first heteroaromatic ring skeleton is a substance including a condensed heteroaromatic ring skeleton.
4. The light-emitting element according to claim 1 ,
wherein the substance including the first heteroaromatic ring skeleton is a substance including a condensed heteroaromatic ring skeleton including a diazine skeleton or a triazine skeleton.
5. The light-emitting element according to claim 1 ,
wherein the substance including the first heteroaromatic ring skeleton is a substance including a pyrazine skeleton or a pyrimidine skeleton.
6. The light-emitting element according to claim 1 ,
wherein the substance including the first heteroaromatic ring skeleton is a substance including a dibenzoquinoxaline skeleton.
7. The light-emitting element according to claim 1 ,
wherein the host material is a substance including an anthracene skeleton.
8. The light-emitting element according to claim 1 ,
wherein the second electron-transport layer is in contact with the cathode.
9. The light-emitting element according to claim 1 ,
wherein the EL layer further comprises a hole-injection layer,
wherein the hole-injection layer is in contact with the anode, and
wherein the hole-injection layer comprises an organic acceptor material.
10. The light-emitting element according to claim 9 ,
wherein the organic acceptor material is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.
11. The light-emitting element according to claim 1 ,
wherein the fluorescent substance exhibits blue light.
12. A light-emitting device comprising:
the light-emitting element according to claim 1 ; and
at least one of a transistor and a substrate.
13. An electronic device comprising:
the light-emitting device according to claim 12 ; and
at least one of a sensor, an operation button, a speaker, and a microphone.
14. A lighting device comprising:
the light-emitting device according to claim 12 ; and
a housing.