Light emitting element and light emitting device and method of manufacturing light emitting element

• US 7,745,019 B2
• Filed: 04/19/2006
• Issued: 06/29/2010
• Est. Priority Date: 04/28/2005
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Nomura, Ryoji, Kato, Kaoru, Arai, Yasuyuki, Yamazaki, Shunpei
• Primary Examiner(s): Tarazano; D. Lawrence
• Assistant Examiner(s): WILSON, MICHAEL H
• Application Number:
  US11/379,322
• Publication Number:
  US 20060243967A1
• Time in Patent Office: 1,532 Days
• Field of Search: 428/690, 428/917, 313/504, 313/506, 257/40, 257 88- 90, 257 94- 97, 257/103, 257/E51.01, 257/E51.017, 257/E51.024, 257E51041-E51044, 252/301.16
• US Class Current: 428/690
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

A light emitting element of the present invention includes a pair of electrodes, a layer containing a composite material, and a light emitting region; wherein the layer containing a composite material contains an organic compound and an inorganic compound; the light emitting region contains a material having a high light emitting property and a material having a high carrier transporting property, and a region containing high concentration of the material having a high light emitting property and a region containing high concentration of the material having a high carrier transporting property are alternately stacked in the light emitting region.

Claims

1. A light emitting device comprising a light emitting element comprising:

a first electrode;

a first layer comprising an organic compound and an inorganic compound over the first electrode; and

a second layer comprising a first, second and third regions over the first layer,

wherein the second region is formed between the first region and the third region,

wherein each of the first, second and third regions comprises a material having a high light emitting property and a material having a high carrier transporting property,

wherein a concentration of the material having a high carrier transporting property is higher than a concentration of the material having a high light emitting property in the first and third regions,

wherein a concentration of the material having a high light emitting property is higher than a concentration of the material having a high carrier transporting property in the second region, and

wherein the concentration of the material having a high light emitting property periodically changes in the second layer.

2. A light emitting device according to claim 1, wherein a highest occupied molecular orbital level of the material having a high light emitting property is higher than a highest occupied molecular orbital level of the material having a high carrier transporting property, and a lowest unoccupied molecular orbital of the material having a high light emitting property is lower than a lowest unoccupied molecular orbital level of the material having a high carrier transporting property.

3. A light emitting device according to claim 1, wherein the second region has a thickness of 20 nm or less.

4. A light emitting device according to claim 1, wherein the second region has a thickness of 5 nm or less.

5. A light emitting device according to claim 1, wherein the first and third regions have a thickness of 20 nm or less.

6. A light emitting device according to claim 1, wherein the first and third regions have a thickness of 5 nm or less.

7. A light emitting device according to claim 1, wherein the material having a high light emitting property fluoresces.

8. A light emitting device according to claim 1, wherein the material having a high light emitting property phosphoresces.

9. A light emitting device according to claim 8, wherein a triplet level of the material having a high light emitting property is lower than a triplet level of the material having a high carrier transporting property.

10. A light emitting device according to claim 1, wherein the material having a high carrier transporting property has an electron transporting property higher than a hole transporting property.

11. A light emitting device according to claim 1, wherein the material having a high carrier transporting property has a hole transporting property higher than an electron transporting property.

12. A light emitting device according to claim 1, wherein the light emitting element further comprises:

a third layer comprising an organic compound and an inorganic compound over the second layer; and

a second electrode over and in contact with the third layer.

13. A light emitting device according to claim 12, wherein the first layer is provided in contact with one of the first and second electrodes.

14. A light emitting device according to claim 1, wherein the inorganic compound is a transition metal oxide.

15. A light emitting device according to claim 1, wherein the inorganic compound is one selected from the group consisting of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide, and a mixture thereof.

16. A light emitting device according to claim 1, wherein the organic compound has hole transporting property.

17. A light emitting device according to claim 1, wherein the organic compound is one of an organic compound having an arylamine skeleton and an organic compound having a carbazole skeleton.

18. A light emitting device comprising a light emitting element comprising:

a first electrode;

a first layer comprising an organic compound and an inorganic compound over the first electrode; and

a second layer comprising a first, second and third regions,

wherein each of the first, second and third regions comprises a material having a high light emitting property and a material having a high carrier transporting property,

wherein a concentration of the material having a high carrier transporting property is higher than a concentration of the material having a high light emitting property in the first and third regions,

wherein the material having a high light emitting property is dispersed in the material having a high carrier transporting property in the second region, and

wherein the concentration of the material having a high light emitting property periodically changes in the second layer.

19. A light emitting device according to claim 18, wherein a highest occupied molecular orbital level of the material having a high light emitting property is higher than a highest occupied molecular orbital level of the material having a high carrier transporting property, and a lowest unoccupied molecular orbital of the material having a high light emitting property is lower than a lowest unoccupied molecular orbital level of the material having a high carrier transporting property.

20. A light emitting device according to claim 18, wherein the second region has a thickness of 20 nm or less.

21. A light emitting device according to claim 18, wherein the second region has a thickness of 5 nm or less.

22. A light emitting device according to claim 18, wherein the first and third regions have a thickness of 20 nm or less.

23. A light emitting device according to claim 18, wherein the first and third regions have a thickness of 5 nm or less.

24. A light emitting device according to claim 18, wherein the second region contains 0.001 wt % to 50 wt % of the material having a high light emitting property.

25. A light emitting device according to claim 18, wherein the second region contains 0.03 wt % to 30 wt % of the material having a high light emitting property.

26. A light emitting device according to claim 18, wherein the material having a high light emitting property fluoresces.

27. A light emitting device according to claim 18, wherein the material having a high light emitting property phosphoresces.

28. A light emitting device according to claim 27, wherein a triplet level of the material having a high light emitting property is lower than a triplet level of the material having a high carrier transporting property.

29. A light emitting device according to claim 18, wherein the material having a high carrier transporting property has an electron transporting property higher than a hole transporting property.

30. A light emitting device according to claim 18, wherein the material having a high carrier transporting property has a hole transporting property higher than an electron transporting property.

31. A light emitting device according to claim 18, wherein the light emitting element further comprises:

a third layer comprising an organic compound and an inorganic compound over the second layer; and

a second electrode over and in contact with the third layer.

32. A light emitting device according to claim 31, wherein the first layer is provided in contact with one of the first and second electrodes.

33. A light emitting device according to claim 18, wherein the inorganic compound is a transition metal oxide.

34. A light emitting device according to claim 18, wherein the inorganic compound is one selected from the group consisting of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide, and a mixture thereof.

35. A light emitting device according to claim 18, wherein the organic compound has hole transporting property.

36. A light emitting device according to claim 18, wherein the organic compound is one of an organic compound having an arylamine skeleton and an organic compound having a carbazole skeleton.