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

1. A light-emitting element comprising:

a mixed layer including a first hole transporting substance and a metal oxide having an electron accepting property to the first hole transporting substance between a first electrode and a second electrode;

a hole transporting layer including a second hole transporting substance over the mixed layer;

a light-emitting layer including a light-emitting substance which emits green light over the hole transporting layer; and

an electron transporting layer including an electron transporting substance over the light-emitting layer;

wherein the mixed layer is in contact with the first electrode,

wherein the mixed layer has a thickness of 120 to 180 nm, and

wherein the metal oxide is included in the mixed layer at a concentration of 7 vol % to 13 vol % with respect to the first hole transporting substance.

2. The light-emitting element according to claim 1 , wherein the first hole transporting substance is one of the group consisting of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene, 4,4′,4″-tris(N-carbazolyl)triphenylamine, or 4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl.

3. The light-emitting element according to claim 1 , wherein the hole transporting layer has a thickness of 5 nm to 50 nm, and wherein the electron transporting layer has a thickness of 5 nm to 30 nm.

4. The light-emitting element according to claim 1 ,

wherein the light-emitting substance emits green light when a voltage is applied between the first electrode and the second electrode such that a potential of the first electrode becomes higher than a potential of the second electrode, and

wherein when an electron mobility of the electron transporting substance used for forming the electron transporting layer and a hole mobility of the first hole transporting substance included in the mixed layer are compared, a ratio of mobility of one substance to mobility of the other substance is 1000 or less.

5. The light-emitting element according to claim 1 , wherein a total film thickness of layers between the light-emitting layer and the first electrode is in a range of 125 nm to 300 nm.

6. The light-emitting element according to claim 1 , wherein a value of a ratio of hole mobility to electron mobility of the first hole transporting substance is larger than 100.

7. A light-emitting device including a pixel portion having the light-emitting element according to claim 1 .

8. An electronic device including a display portion having the light-emitting device according to claim 7 , wherein the electronic device is selected from the group consisting of a personal computer, a portable phone, a television, a navigation system and a lighting system.

9. The light-emitting element according to claim 1 , wherein at least one of the second hole transporting substance and the electron transporting substance is a bipolar substance.

10. The light-emitting element according to claim 9 , wherein the bipolar substance is one of the group consisting of 2,3-bis(4-diphenylaminophenyl)quinoxaline or 2,3-bis{4-[N-(1-naphythyl)-N-phenylamino]phenyl}-dibenzo[f,h]quinoxaline.

11. The light-emitting element according to claim 9 , wherein the second hole transporting layer and the electron transporting layer are formed of the same bipolar substance.

12. A light-emitting element comprising:

a mixed layer including a first hole transporting substance and a metal oxide having an electron accepting property to the first hole transporting substance between a first electrode and a second electrode;

a hole transporting layer including a second hole transporting substance over the mixed layer;

a light-emitting layer including a light-emitting substance and a substance to disperse the light-emitting substance over the hole transporting layer; and

an electron transporting layer including an electron transporting substance over the light-emitting layer;

wherein the mixed layer is in contact with the first electrode,

wherein the mixed layer has a thickness of 120 to 180 nm, and

wherein the metal oxide is included in the mixed layer at a concentration of 7 vol % to 13 vol % with respect to the first hole transporting substance.

13. The light-emitting element according to claim 12 , wherein the first hole transporting substance is one of the group consisting of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene, 4,4′,4″-tris(N-carbazolyl)triphenylamine, or 4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl.

14. The light-emitting element according to claim 12 , wherein the hole transporting layer has a thickness of 5 nm to 50 nm, and wherein the electron transporting layer has a thickness of 5 nm to 30 nm.

15. The light-emitting element according to claim 12 ,

wherein the light-emitting substance emits green light when a voltage is applied between the first electrode and the second electrode such that a potential of the first electrode becomes higher than a potential of the second electrode, and

wherein when an electron mobility of the electron transporting substance used for forming the electron transporting layer and a hole mobility of the first hole transporting substance included in the mixed layer are compared, a ratio of mobility of one substance to mobility of the other substance is 1000 or less.

16. The light-emitting element according to claim 12 , wherein a total film thickness of layers between the light-emitting layer and the first electrode is in a range of 125 nm to 300 nm.

17. The light-emitting element according to claim 12 , wherein the substance to disperse the light-emitting substance is selected from a metal complex, an anthracene derivative, a carbazole derivative, and a quinoxaline derivative.

18. The light-emitting element according to claim 12 , wherein a value of a ratio of hole mobility to electron mobility of the first hole transporting substance is larger than 100.

19. A light-emitting device including a pixel portion having the light-emitting element according to claim 12 .

20. An electronic device including a display portion having the light-emitting device according to claim 19 , wherein the electronic device is selected from the group consisting of a personal computer, a portable phone, a television, a navigation system and a lighting system.

21. The light-emitting element according to claim 12 , wherein at least one of the second hole transporting substance and the electron transporting substance is a bipolar substance.

22. The light-emitting element according to claim 21 , wherein the bipolar substance is one of the group consisting of 2,3-bis(4-diphenylaminophenyl)quinoxaline or 2,3-bis{4-[N-(1-naphythyl)-N-phenylamino]phenyl}-dibenzo[f,h]quinoxaline.

23. The light-emitting element according to claim 21 , wherein the second hole transporting layer and the electron transporting layer are formed of the same bipolar substance.

24. A light-emitting element comprising:

a mixed layer including a first hole transporting substance and a molybdenum oxide between a first electrode and a second electrode;

a hole transporting layer including a second hole transporting substance over the mixed layer;

a light-emitting layer including a light-emitting substance which emits green light over the hole transporting layer; and

an electron transporting layer including an electron transporting substance over the light-emitting layer;

wherein the mixed layer is in contact with the first electrode,

wherein the mixed layer has a thickness of 120 to 180 nm, and

wherein the molybdenum oxide is included in the mixed layer at a concentration of 7 vol % to 13 vol % with respect to the first hole transporting substance.

25. The light-emitting element according to claim 24 , wherein the first hole transporting substance is one of the group consisting of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene, 4,4′,4″-tris(N-carbazolyl)triphenylamine, or 4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl.

26. The light-emitting element according to claim 24 , wherein the hole transporting layer has a thickness of 5 nm to 50 nm, and wherein the electron transporting layer has a thickness of 5 nm to 30 nm.

27. The light-emitting element according to claim 24 ,

wherein the light-emitting substance emits green light when a voltage is applied between the first electrode and the second electrode such that a potential of the first electrode becomes higher than a potential of the second electrode, and

wherein when an electron mobility of the electron transporting substance used for forming the electron transporting layer and a hole mobility of the first hole transporting substance included in the mixed layer are compared, a ratio of mobility of one substance to mobility of the other substance is 1000 or less.

28. The light-emitting element according to claim 24 , wherein a total film thickness of layers between the light-emitting layer and the first electrode is in a range of 125 nm to 300 nm.

29. The light-emitting element according to claim 24 , wherein a value of a ratio of hole mobility to electron mobility of the first hole transporting substance is larger than 100.

30. A light-emitting device including a pixel portion having the light-emitting element according to claim 24 .

31. An electronic device including a display portion having the light-emitting device according to claim 30 , wherein the electronic device is selected from the group consisting of a personal computer, a portable phone, a television, a navigation system and a lighting system.

32. The light-emitting element according to claim 24 , wherein at least one of the second hole transporting substance and the electron transporting substance is a bipolar substance.

33. The light-emitting element according to claim 32 , wherein the bipolar substance is one of the group consisting of 2,3-bis(4-diphenylaminophenyl)quinoxaline or 2,3-bis{4-[N-(1-naphythyl)-N-phenylamino]phenyl}-dibenzo[f,h]quinoxaline.

34. The light-emitting element according to claim 32 , wherein the second hole transporting layer and the electron transporting layer are formed of the same bipolar substance.

35. A light-emitting element comprising:

a mixed layer including a first hole transporting substance and a molybdenum oxide between a first electrode and a second electrode;

a hole transporting layer including a second hole transporting substance over the mixed layer;

a light-emitting layer including a light-emitting substance and a substance to disperse the light-emitting substance over the hole transporting layer; and

an electron transporting layer including an electron transporting substance over the light-emitting layer;

wherein the mixed layer is in contact with the first electrode,

wherein the mixed layer has a thickness of 120 to 180 nm, and

wherein the molybdenum oxide is included in the mixed layer at a concentration of 7 vol % to 13 vol % with respect to the first hole transporting substance.

36. The light-emitting element according to claim 35 , wherein the first hole transporting substance is one of the group consisting of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene, 4,4′,4″-tris(N-carbazolyl)triphenylamine, or 4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl.

37. The light-emitting element according to claim 35 , wherein the hole transporting layer has a thickness of 5 nm to 50 nm, and wherein the electron transporting layer has a thickness of 5 nm to 30 nm.

38. The light-emitting element according to claim 35 ,

wherein the light-emitting substance emits green light when a voltage is applied between the first electrode and the second electrode such that a potential of the first electrode becomes higher than a potential of the second electrode, and

wherein when an electron mobility of the bipolar electron transporting substance used for forming the electron transporting layer and a hole mobility of the first hole transporting substance included in the mixed layer are compared, a ratio of mobility of one substance to mobility of the other substance is 1000 or less.

39. The light-emitting element according to claim 35 , wherein a total film thickness of layers between the light-emitting layer and the first electrode is in a range of 125 nm to 300 nm.

40. The light-emitting element according to claim 35 , wherein the substance to disperse the light-emitting substance is selected from a metal complex, an anthracene derivative, a carbazole derivative, and a quinoxaline derivative.

41. The light-emitting element according to claim 35 , wherein a value of a ratio of hole mobility to electron mobility of the first hole transporting substance is larger than 100.

42. A light-emitting device including a pixel portion having the light-emitting element according to claim 35 .

43. An electronic device including a display portion having the light-emitting device according to claim 42 , wherein the electronic device is selected from the group consisting of a personal computer, a portable phone, a television, a navigation system and a lighting system.

44. The light-emitting element according to claim 35 , wherein at least one of the second hole transporting substance and the electron transporting substance is a bipolar substance.

45. The light-emitting element according to claim 44 , wherein the bipolar substance is one of the group consisting of 2,3-bis(4-diphenylaminophenyl)quinoxaline or 2,3-bis{4-[N-(1-naphythyl)-N-phenylamino]phenyl}-dibenzo[f,h]quinoxaline.

46. The light-emitting element according to claim 44 , wherein the second hole transporting layer and the electron transporting layer are formed of the same bipolar substance.

47. A light-emitting element comprising:

a mixed layer including a first hole transporting substance and a molybdenum trioxide between a first electrode and a second electrode;

a hole transporting layer including a second hole transporting substance over the mixed layer;

a light-emitting layer including a light-emitting substance which emits green light over the hole transporting layer; and

an electron transporting layer including an electron transporting substance over the light-emitting layer;

wherein the mixed layer is in contact with the first electrode,

wherein the mixed layer has a thickness of 120 to 180 nm, and

wherein the molybdenum trioxide oxide is included in the mixed layer at a concentration of 7 vol % to 13 vol % with respect to the first hole transporting substance.

48. The light-emitting element according to claim 47 , wherein the first hole transporting substance is one of the group consisting of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene, 4,4′,4″-tris(N-carbazolyl)triphenylamine, or 4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl.

49. The light-emitting element according to claim 47 , wherein the hole transporting layer has a thickness of 5 nm to 50 nm, and wherein the electron transporting layer has a thickness of 5 nm to 30 nm.

50. The light-emitting element according to claim 47 ,

wherein the light-emitting substance emits green light when a voltage is applied between the first electrode and the second electrode such that a potential of the first electrode becomes higher than a potential of the second electrode, and

wherein when an electron mobility of the electron transporting substance used for forming the electron transporting layer and a hole mobility of the first hole transporting substance included in the mixed layer are compared, a ratio of mobility of one substance to mobility of the other substance is 1000 or less.

51. The light-emitting element according to claim 47 , wherein a total film thickness of layers between the light-emitting layer and the first electrode is in a range of 125 nm to 300 nm.

52. The light-emitting element according to claim 47 , wherein a value of a ratio of hole mobility to electron mobility of the first hole transporting substance is larger than 100.

53. A light-emitting device including a pixel portion having the light-emitting element according to claim 47 .

54. An electronic device including a display portion having the light-emitting device according to claim 53 , wherein the electronic device is selected from the group consisting of a personal computer, a portable phone, a television, a navigation system and a lighting system.

55. The light-emitting element according to claim 47 , wherein at least one of the second hole transporting substance and the electron transporting substance is a bipolar substance.

56. The light-emitting element according to claim 55 , wherein the bipolar substance is one of the group consisting of 2,3-bis(4-diphenylaminophenyl)quinoxaline or 2,3-bis{4-[N-(1-naphythyl)-N-phenylamino]phenyl}-dibenzo[f,h]quinoxaline.

57. The light-emitting element according to claim 55 , wherein the second hole transporting layer and the electron transporting layer are formed of the same bipolar substance.

58. A light-emitting element comprising:

a mixed layer including a first hole transporting substance and a molybdenum trioxide between a first electrode and a second electrode;

a hole transporting layer including a second hole transporting substance over the mixed layer;

a light-emitting layer including a light-emitting substance and a substance to disperse the light-emitting substance over the hole transporting layer; and

an electron transporting layer including an electron transporting substance over the light-emitting layer;

wherein the mixed layer is in contact with the first electrode,

wherein the mixed layer has a thickness of 120 to 180 nm, and

wherein the molybdenum trioxide oxide is included in the mixed layer at a concentration of 7 vol % to 13 vol % with respect to the first hole transporting substance.

59. The light-emitting element according to claim 58 , wherein the first hole transporting substance is one of the group consisting of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl, 1,3,5-tris[N,N-di(m-tolyl)amino]benzene, 4,4′,4″-tris(N-carbazolyl)triphenylamine, or 4,4′-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl.

60. The light-emitting element according to claim 58 , wherein the hole transporting layer has a thickness of 5 nm to 50 nm, and wherein the electron transporting layer has a thickness of 5 nm to 30 nm.

61. The light-emitting element according to claim 58 ,

wherein the light-emitting substance emits green light when a voltage is applied between the first electrode and the second electrode such that a potential of the first electrode becomes higher than a potential of the second electrode, and

wherein when an electron mobility of the electron transporting substance used for forming the electron transporting layer and a hole mobility of the first hole transporting substance included in the mixed layer are compared, a ratio of mobility of one substance to mobility of the other substance is 1000 or less.

62. The light-emitting element according to claim 58 , wherein a total film thickness of layers between the light-emitting layer and the first electrode is in a range of 125 nm to 300 nm.

63. The light-emitting element according to claim 58 , wherein the substance to disperse the light-emitting substance is selected from a metal complex, an anthracene derivative, a carbazole derivative, and a quinoxaline derivative.

64. The light-emitting element according to claim 58 , wherein a value of a ratio of hole mobility to electron mobility of the first hole transporting substance is larger than 100.

65. A light-emitting device including a pixel portion having the light-emitting element according to claim 58 .

66. An electronic device including a display portion having the light-emitting device according to claim 65 , wherein the electronic device is selected from the group consisting of a personal computer, a portable phone, a television, a navigation system and a lighting system.

67. The light-emitting element according to claim 58 , wherein at least one of the second hole transporting substance and the electron transporting substance is a bipolar substance.

68. The light-emitting element according to claim 67 , wherein the bipolar substance is one of the group consisting of 2,3-bis(4-diphenylaminophenyl)quinoxaline or 2,3-bis{4-[N-(1-naphythyl)-N-phenylamino]phenyl}-dibenzo[f,h]quinoxaline.

69. The light-emitting element according to claim 67 , wherein the second hole transporting layer and the electron transporting layer are formed of the same bipolar substance.