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

Abstract

It is an object to provide an element structure which is suitable for a light-emitting element using a phosphorescent compound. It is another object to provide a light-emitting element with high luminous efficiency by using the element structure. In particular, it is another object to provide a light-emitting element with high luminous efficiency and long life. A light-emitting element is manufactured, which includes a first light-emitting layer and a second light-emitting layer provided to be in contact with each other between a first electrode and a second electrode, where the first light-emitting layer includes a hole transporting host material and a phosphorescent compound, and the second light-emitting layer includes an electron transporting host material and the phosphorescent compound.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is an explanatory view of an element structure of a light-emitting element of the present invention;

FIG. 2 is an explanatory view of an element structure of a light-emitting element of the present invention;

FIGS. 3A and 3B are explanatory views of an element structure of a conventional light-emitting element;

FIGS. 4A to 4C are explanatory views of a light-emitting device using a light-emitting element of the present invention;

FIGS. 5A to 5C are explanatory views of an electronic device using a light-emitting device of the present invention;

FIGS. 6A and 6B are graphs each showing an ¹H NMR chart of an oxadiazole derivative CO11;

FIGS. 7A and 7B are graphs each showing an ultraviolet-visible spectrum and emission spectrum of an oxadiazole derivative CO11;

FIGS. 8A and 8B are views each showing operation characteristics of light-emitting elements manufactured in Example 2;

FIG. 9 is a view showing operation characteristics of light-emitting elements manufactured in Example 2;

FIGS. 10A and 10B are views each showing operation characteristics of light-emitting elements manufactured in Example 3;

FIG. 11 is a view showing operation characteristics of light-emitting elements manufactured in Example 3;

FIGS. 12A and 12B are views each showing operation characteristics of light-emitting elements manufactured in Example 4;

FIG. 13 is a view showing operation characteristics of light-emitting elements manufactured in Example 4;

FIGS. 14A and 14B are views each showing operation characteristics of light-emitting elements manufactured in Example 6;

FIG. 15 is a view showing operation characteristics of light-emitting elements manufactured in Example 6;

FIGS. 16A and 16B are views each showing operation characteristics of light-emitting elements manufactured in Example 7; and

FIG. 17 is a view showing operation characteristics of light-emitting elements manufactured in Example 7.

Claims

1. A light-emitting element comprising: a first light-emitting layer and a second light-emitting layer being in contact with each other between a first electrode and a second electrode,wherein the first light-emitting layer comprises a hole transporting host material and a phosphorescent compound, and the second light-emitting layer comprises an electron transporting host material and the phosphorescent compound.

2. The light-emitting element according to claim 1, further comprising: a hole transporting layer formed between the first electrode and the first light-emitting layer and being in contact with the first light-emitting layer,wherein the hole transporting layer has triplet excitation energy lower than that of the phosphorescent compound.

3. The light-emitting element according to claim 1, further comprising: an electron transporting layer formed between the second electrode and the second light-emitting layer and being in contact with the second light-emitting layer,wherein the electron transporting layer has triplet excitation energy lower than that of the phosphorescent compound.

4. The light-emitting element according to claim 1, wherein the hole transporting host material is an aromatic amine compound.

5. The light-emitting element according to claim 1, wherein the hole transporting host material is a triaryl amine compound.

6. The light-emitting element according to claim 1, wherein the electron transporting host material is a heteroaromatic compound.

7. The light-emitting element according to claim 1, wherein the electron transporting host material is a material selected from the group consisting of an oxadiazole derivative, an oxazole derivative, an imidazole derivative, a triazole derivative, and a triazine derivative.

8. The light-emitting element according to claim 1, wherein the electron transporting host material is an oxadiazole derivative represented by the following structural formula (1).

9. The light-emitting element according to claim 1, wherein an emission wavelength of the phosphorescent compound is greater than or equal to 450 nm and less than or equal to 540 nm.

10. The light-emitting element according to claim 1, wherein the phosphorescent compound is a guest material.

11. The light-emitting element according to claim 1, wherein energy gap of the electron transporting host material is 3.3 eV or less.

12. An electronic device having the light-emitting element according to claim 1, wherein the electronic device is one selected from the group consisting of a computer, telephone, television set, a navigation system, and a lighting apparatus.

13. A light-emitting element comprising: a first light-emitting layer including a hole transporting host material and a phosphorescent compound formed over a first electrode;a second light-emitting layer including an electron transporting host material and the phosphorescent compound formed on and being in contact with the first light-emitting layer; anda second electrode formed over the second light-emitting layer.

14. The light-emitting element according to claim 13, further comprising: a hole transporting layer formed between the first electrode and the first light-emitting layer and being in contact with the first light-emitting layer,wherein the hole transporting layer has triplet excitation energy lower than that of the phosphorescent compound.

15. The light-emitting element according to claim 13, further comprising: an electron transporting layer formed between the second electrode and the second light-emitting layer and being in contact with the second light-emitting layer,wherein the electron transporting layer has triplet excitation energy lower than that of the phosphorescent compound.

16. The light-emitting element according to claim 13, wherein the hole transporting host material is an aromatic amine compound.

17. The light-emitting element according to claim 13, wherein the hole transporting host material is a triaryl amine compound.

18. The light-emitting element according to claim 13, wherein the electron transporting host material is a heteroaromatic compound.

19. The light-emitting element according to claim 13, wherein the electron transporting host material is a material selected from the group consisting of an oxadiazole derivative, an oxazole derivative, an imidazole derivative, a triazole derivative, and a triazine derivative.

20. The light-emitting element according to claim 13, wherein the electron transporting host material is an oxadiazole derivative represented by the following structural formula (1).

21. The light-emitting element according to claim 13, wherein an emission wavelength of the phosphorescent compound is greater than or equal to 450 nm and less than or equal to 540 nm.

22. The light-emitting element according to claim 13, wherein the phosphorescent compound is a guest material.

23. The light-emitting element according to claim 13, wherein energy gap of the electron transporting host material is 3.3 eV or less.

24. An electronic device having the light-emitting element according to claim 13, wherein the electronic device is one selected from the group consisting of a computer, telephone, television set, a navigation system, and a lighting apparatus.