Light emitting device

• US 20010045565A1
• Filed: 06/04/2001
• Published: 11/29/2001
• Est. Priority Date: 06/05/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Granted Patent: US 7,339,317 B2
• Time in Patent Office: Days
• US Class Current: 257/89
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2102/00 Constructional details relating to the organic devices covered by this subclass
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/828 Transparent cathodes, e.g. comprising thin metal layers
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/122 Pixel-defining structures or layers, e.g. banks
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/35 comprising red-green-blue [RGB] subpixels
• CPC Class Codes: H10K 85/30 Coordination compounds
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/346 comprising platinum
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

There is provided a light emitting device which enables a color display with good color balance. A triplet compound is used for a light emitting layer of an EL element that emits red color, and a singlet compound is used for a light emitting layer of an EL element that emits green color and a light emitting layer of an EL element that emits blue color. Thus, an operation voltage of the EL element emitting red color may be made the same as the EL element emitting green color and the EL element emitting blue color. Accordingly, the color display with good color balance can be realized.

Claims

1. A light emitting device comprising:

a pixel portion;

a switching thin film transistor in the pixel portion;

a current control thin film transistor in the pixel portion;

at least an EL element electrically connected to the current control thin film transistor in the pixel portion;

wherein the switching thin film transistor is an n-channel thin film transistor;

wherein the current control thin film transistor is a p-channel thin film transistor;

a first pixel including a first EL element for emitting a red light in the pixel portion;

a second pixel including a second EL element for emitting a green light in the pixel portion;

a third pixel including a third EL element for emitting a blue light in the pixel portion;

wherein a triplet compound is used in the first EL element while a singlet compound is used in each of the second and third EL elements.

5. A device according to

claim 1

,

wherein the triplet compound is represented by

6. A device according to

claim 1

,

wherein the triplet compound is represented by

7. A device according to

claim 5

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

8. A device according to

claim 1

,

wherein each of the switching thin film transistor and the current control thin film transistor is a bottom gate thin film transistor.

9. A device according to

claim 1

,

wherein each of the switching thin film transistor and the current control thin film transistor is an inverted stagger thin film transistor.

10. A module using the light emitting device of

claim 1

.

11. An electrical apparatus using the light emitting device of

claim 1

.

12. A portable telephone using the light emitting device of

claim 1

.

13. A digital camera using the light emitting device of

claim 1

.

14. An audio equipment using the light emitting device of

claim 1

.

15. A method of operating the EL element of

claim 1

in a range of 10V or less.

19. A device according to

claim 6

,

where in the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

2. A light emitting device comprising:

a pixel portion;

a switching thin film transistor in the pixel portion;

a current control thin film transistor in the pixel portion;

at least an EL element electrically connected to the current control thin film transistor in the pixel portion;

wherein the switching thin film transistor is a p-channel thin film transistor;

wherein the current control thin film transistor is an n-channel thin film transistor;

a first pixel including a first EL element for emitting a red light in the pixel portion;

a second pixel including a second EL element for emitting a green light in the pixel portion;

a third pixel including a third EL element for emitting a blue light in the pixel portion;

wherein a triplet compound is used in the first EL element while a singlet compound is used in each of the second and third EL elements.

16. A method of operating the EL element of

claim 2

in a range of 10V or less.

20. A device according to

claim 2

,

wherein the triplet compound is represented by

21. A device according to

claim 2

,

wherein the triplet compound is represented by

22. A device according to

claim 20

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

23. A device according to

claim 21

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

24. A device according to

claim 2

,

wherein each of the switching thin film transistor and the current control thin film transistor is a bottom gate thin film transistor.

25. A device according to

claim 2

,

wherein each of the switching thin film transistor and the current control thin film transistor is an inverted stagger thin film transistor.

26. A module using the light emitting device of

claim 2

.

27. An electrical apparatus using the light emitting device of

claim 2

.

28. A portable telephone using the light emitting device of

claim 2

.

29. A digital camera using the light emitting device of

claim 2

.

30. An audio equipment using the light emitting device of

claim 2

.

3. A light emitting device comprising:

a pixel portion;

a switching thin film transistor in the pixel portion;

a current control thin film transistor in the pixel portion;

at least an EL element electrically connected to the current control thin film transistor in the pixel portion;

wherein the switching thin film transistor is an n-channel thin film transistor;

wherein the current control thin film transistor is an n-channel thin film transistor;

a first pixel including a first EL element for emitting a red light in the pixel portion;

a second pixel including a second EL element for emitting a green light in the pixel portion;

a third pixel including a third EL element for emitting a blue light in the pixel portion;

wherein a triplet compound is used in the first EL element while a singlet compound is used in each of the second and third EL elements.

17. A method of operating the EL element of

claim 3

in a range of 10V or less.

31. A device according to

claim 3

,

wherein the triplet compound is represented by

32. A device according to

claim 3

,

wherein the triplet compound is represented by

33. A device according to

claim 31

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

34. A device according to

claim 32

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

35. A device according to

claim 3

,

wherein each of the switching thin film transistor and the current control thin film transistor is a bottom gate thin film transistor.

36. A device according to

claim 3

,

wherein each of the switching thin film transistor and the current control thin film transistor is an inverted stagger thin film transistor.

37. A module using the light emitting device of

claim 3

.

38. An electrical apparatus using the light emitting device of

claim 3

.

39. A portable telephone using, the light emitting device of

claim 3

.

40. A digital camera using the light emitting device of

claim 3

.

41. An audio equipment using the light emitting device of

claim 3

.

4. A light emitting device comprising:

a pixel portion;

a switching thin film transistor in the pixel portion;

a current control thin film transistor in the pixel portion;

at least an EL element electrically connected to the current control thin film transistor in the pixel portion;

wherein the switching thin film transistor is a p-channel thin film transistor;

wherein the current control thin film transistor is a p-channel thin film transistor;

a first pixel including a first EL element for emitting a red light in the pixel portion;

a second pixel including a second EL element for emitting a green light in the pixel portion;

a third pixel including a third EL element for emitting a blue light in the pixel portion;

wherein a triplet compound is used in the first EL element while a singlet compound is used in each of the second and third EL elements.

18. A method of operating the EL element of

claim 4

in a range of 10V or less.

42. A device according to

claim 4

,

wherein the triplet compound is represented by

43. A device according to

claim 4

,

wherein the triplet compound is represented by

44. A device according to

claim 42

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

45. A device according to

claim 43

,

wherein the element belonging to Groups 8-10 in the periodic table is one selected from the group consisting of platinum, iridium, nickel, cobalt and palladium.

46. A device according to

claim 4

,

wherein each of the switching thin film transistor and the current control thin film transistor is a bottom gate thin film transistor.

47. A device according to

claim 4

,

wherein each of the switching thin film transistor and the current control thin film transistor is an inverted stagger thin film transistor.

48. A module using the light emitting device of

claim 4

.

49. An electrical apparatus using the light emitting device of

claim 4

.

50. A portable telephone using the light emitting device of

claim 4

.

51. A digital camera using the light emitting device of

claim 4

.

52. An audio equipment using the light emitting device of

claim 4

.