Light-emitting element, light-emitting device, electronic device, and lighting device

1. A light-emitting element comprising:

a first electrode;

an EL layer over the first electrode, the EL layer comprising:

a hole-injection layer being in contact with the first electrode;

a first hole-transport layer being in contact with the hole-injection layer;

a second hole-transport layer over the first hole-transport layer;

a third hole-transport layer;

a light-emitting layer being in contact with the third hole-transport layer;

a first electron-transport layer over and in contact with the light-emitting layer; and

a second electron-transport layer being in contact with the first electron-transport layer; and

a second electrode over the EL layer,

wherein the hole-injection layer, the first hole-transport layer, the second hole-transport layer and the third hole-transport layer are positioned between the first electrode and the light-emitting layer,

wherein the second hole-transport layer is positioned between the first hole-transport layer and the third hole-transport layer,

wherein the first electron-transport layer and the second electron-transport layer are positioned between the light-emitting layer and the second electrode,

wherein the hole-injection layer comprises an organic acceptor,

wherein the first hole-transport layer comprises a first hole-transport material,

wherein the second hole-transport layer comprises a second hole-transport material,

wherein the third hole-transport layer comprises a third hole-transport material,

wherein the light-emitting layer comprises a host material and a light-emitting material,

wherein the first electron-transport layer comprises a first electron-transport material,

wherein the second electron-transport layer comprises a second electron-transport material,

wherein a difference between a LUMO level of the organic acceptor and a HOMO level of the first hole-transport material is less than or equal to 1 eV,

wherein a HOMO level of the second hole-transport material is lower than the HOMO level of the first hole-transport material,

wherein a HOMO level of the host material is lower than the HOMO level of the second hole-transport material,

wherein a HOMO level of the third hole-transport material is lower than or equal to the HOMO level of the host material,

wherein a difference between the HOMO level of the second hole-transport material and the HOMO level of the third hole-transport material is less than or equal to 0.3 eV,

wherein a LUMO level of the host material is higher than a LUMO level of the first electron-transport material,

wherein a LUMO level of the second electron-transport material is higher than the LUMO level of the first electron-transport material,

wherein the host material is a substance including a condensed aromatic ring skeleton including 3 to 6 rings,

wherein the first electron-transport material is a substance having a first heteroaromatic ring skeleton,

wherein the second electron-transport material is a substance having a second heteroaromatic ring skeleton, and

wherein the first heteroaromatic ring skeleton and the second heteroaromatic ring skeleton are different from each other.

2. The light-emitting element according to claim 1 , wherein the light-emitting material is a fluorescent material.

3. The light-emitting element according to claim 1 , wherein the light-emitting material is a condensed aromatic diamine compound.

4. The light-emitting element according to claim 1 , wherein the organic acceptor is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.

5. The light-emitting element according to claim 1 , wherein the host material has an anthracene skeleton.

6. 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.

7. 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.

8. The light-emitting element according to claim 1 , wherein the substance including the first heteroaromatic ring skeleton is a substance including a dibenzoquinoxaline skeleton.

9. A light-emitting device comprising:

the light-emitting element according to claim 1 ; and

a transistor or a substrate.

10. An electronic device comprising:

the light-emitting device according to claim 9 ; and

one selected from a sensor, an operation button, a speaker and a microphone.

11. A light-emitting element comprising:

a first electrode;

a hole-injection layer over the first electrode, the hole-injection layer comprising an organic acceptor;

a hole-transport layer over the hole-injection layer, the hole-transport layer comprising a hole-transport material;

a light-emitting layer over the hole-transport layer, the light-emitting layer comprising a host material and a light-emitting material;

a first electron-transport layer over the light-emitting layer, the first electron-transport layer comprising a first electron-transport material;

a second electron-transport layer over the first electron-transport layer, the second electron-transport layer comprising a second electron-transport material; and

a second electrode over the second electron-transport layer,

wherein a difference between a LUMO level of the organic acceptor and a HOMO level of the hole-transport material is less than or equal to 1 eV,

wherein a LUMO level of the host material is higher than a LUMO level of the first electron-transport material,

wherein a LUMO level of the second electron-transport material is higher than the LUMO level of the first electron-transport material,

wherein the host material has a condensed aromatic ring skeleton including 3 to 6 rings,

wherein the first electron-transport material has a first heteroaromatic ring skeleton,

wherein the second electron-transport material has a second heteroaromatic ring skeleton, and

wherein the first heteroaromatic ring skeleton and the second heteroaromatic ring skeleton are different from each other.

12. The light-emitting element according to claim 11 , wherein the light-emitting material is a fluorescent material.

13. The light-emitting element according to claim 11 , wherein the light-emitting material is a condensed aromatic diamine compound.

14. The light-emitting element according to claim 11 , wherein the organic acceptor is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.

15. The light-emitting element according to claim 11 , wherein the host material has an anthracene skeleton.

16. The light-emitting element according to claim 11 , wherein the first heteroaromatic ring skeleton is a condensed heteroaromatic ring skeleton.

17. The light-emitting element according to claim 11 , wherein the first heteroaromatic ring skeleton is a pyrazine skeleton or a pyrimidine skeleton.

18. The light-emitting element according to claim 11 , wherein the first heteroaromatic ring skeleton is a dibenzoquinoxaline skeleton.

19. The light-emitting element according to claim 11 ,

wherein the first heteroaromatic ring skeleton is a condensed heteroaromatic ring skeleton including a diazine skeleton or a triazine skeleton, and

wherein the second heteroaromatic ring skeleton comprises one of a pyridine skeleton and a bipyridine.

20. The light-emitting element according to claim 19 , wherein the second heteroaromatic ring skeleton is a phenanthroline skeleton.

21. A light-emitting device comprising:

the light-emitting element according to claim 11 ; and

a transistor electrically connected to the light-emitting element.

22. An electronic device comprising:

the light-emitting device according to claim 21 ,

wherein the electronic device is any one of a television device, a monitor, a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, an audio reproducing device, and a game machine.