Light-emitting device having light emission by a singlet exciton and a triplet exciton
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.
1. An active matrix type light emitting device comprising a pixel portion comprising:
a first pixel which emits red light comprising:
a first EL element comprising a hole injecting layer and a light emitting layer between a first electrode and a second electrode;
a first current controlling TFT electrically connected to the first electrode, wherein the first current controlling TFT is configured to control a current flowing in the first EL element;
a first switching TFT configured to control a signal to be input to a gate electrode of the first current controlling TFT; and
a first capacitor electrically connected to the gate electrode of the first current controlling TFT, wherein the first capacitor is configured to maintain a voltage applied to the gate electrode of the first current controlling TFT;
a second pixel which emits green light comprising:
a second EL element comprising a hole injecting layer and a light emitting layer between a third electrode and a fourth electrode;
a second current controlling TFT electrically connected to the third electrode, wherein the second current controlling TFT is configured to control a current flowing in the second EL element;
a second switching TFT configured to control a signal to be input to a gate electrode of the second current controlling TFT; and
a second capacitor electrically connected to the gate electrode of the second current controlling TFT, wherein the second capacitor is configured to maintain a voltage applied to the gate electrode of the second current controlling TFT;
a third pixel which emits blue light comprising:
a third EL element comprising a hole injecting layer and a light emitting layer between a fifth electrode and a sixth electrode;
a third current controlling TFT electrically connected to the fifth electrode, wherein the third current controlling TFT is configured to control a current flowing in the third EL element;
a third switching TFT configured to control a signal to be input to a gate electrode of the third current controlling TFT; and
a third capacitor electrically connected to the gate electrode of the third current controlling TFT, wherein the third capacitor is configured to maintain a voltage applied to the gate electrode of the third current controlling TFT;
an insulating film over the first current controlling TFT, the second current controlling TFT, and the third current controlling TFT,
wherein the insulating film comprises a first opening, a second opening, and a third opening,
wherein the first electrode overlaps with the first opening,
wherein the third electrode overlaps with the second opening,
wherein the fifth electrode overlaps with the third opening,
wherein an upper surface of the insulating film is provided over an upper surface of the first electrode, an upper surface of the third electrode, and an upper surface of the fifth electrode,
wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are provided as a common layer,
wherein the second electrode, the fourth electrode, and the sixth electrode are provided as a common layer,
wherein the first EL element included in the first pixel which emits red light is configured to emit light by a triplet exciton,
wherein the third EL element included in the third pixel which emits blue light is configured to emit light by a singlet exciton, and
wherein an operation voltage of the first EL element, an operation voltage of the second EL element, and an operation voltage of the third EL element are in a range of 10 V or less.
2. The active matrix type light emitting device according to claim 1 , wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are continuously formed.
3. The active matrix type light emitting device according to claim 1 ,
wherein the first EL element further comprises an electron transporting layer between the first electrode and the second electrode,
wherein the second EL element further comprises an electron transporting layer between the third electrode and the fourth electrode,
wherein the third EL element further comprises an electron transporting layer between the fifth electrode and the sixth electrode, and
wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are provided as a common layer.
4. The active matrix type light emitting device according to claim 3 , wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are continuously formed.
5. The active matrix type light emitting device according to claim 1 , wherein the first electrode, the third electrode, the fifth electrode each comprises an oxide conductive film which transmits visible light.
6. An active matrix type light emitting device comprising a pixel portion comprising:
a first pixel which emits red light comprising:
a first EL element comprising a hole injecting layer and a light emitting layer between a first electrode and a second electrode;
a first current controlling TFT electrically connected to the first electrode, wherein the first current controlling TFT is configured to control a current flowing in the first EL element;
a first switching TFT configured to control a signal to be input to a gate electrode of the first current controlling TFT; and
a first capacitor electrically connected to the gate electrode of the first current controlling TFT, wherein the first capacitor is configured to maintain a voltage applied to the gate electrode of the first current controlling TFT;
a second pixel which emits green light comprising:
a second EL element comprising a hole injecting layer and a light emitting layer between a third electrode and a fourth electrode;
a second current controlling TFT electrically connected to the third electrode, wherein the second current controlling TFT is configured to control a current flowing in the second EL element;
a second switching TFT configured to control a signal to be input to a gate electrode of the second current controlling TFT; and
a second capacitor electrically connected to the gate electrode of the second current controlling TFT, wherein the second capacitor is configured to maintain a voltage applied to the gate electrode of the second current controlling TFT;
a third pixel which emits blue light comprising:
a third EL element comprising a hole injecting layer and a light emitting layer between a fifth electrode and a sixth electrode;
a third current controlling TFT electrically connected to the fifth electrode, wherein the third current controlling TFT is configured to control a current flowing in the third EL element;
a third switching TFT configured to control a signal to be input to a gate electrode of the third current controlling TFT; and
a third capacitor electrically connected to the gate electrode of the third current controlling TFT, wherein the third capacitor is configured to maintain a voltage applied to the gate electrode of the third current controlling TFT;
a leveling film over the first current controlling TFT, the second current controlling TFT, and the third current controlling TFT; and
an insulating film covering with an end portion of the first electrode, an end portion of the third electrode, and an end portion of the fifth electrode,
wherein the insulating film comprises a first opening, a second opening, and a third opening,
wherein the first electrode overlaps with the first opening and is provided over the leveling film,
wherein the third electrode overlaps with the second opening and is provided over the leveling film,
wherein the fifth electrode overlaps with the third opening and is provided over the leveling film,
wherein an upper surface of the insulating film is provided over an upper surface of the first electrode, an upper surface of the third electrode, and an upper surface of the fifth electrode,
wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are provided as a common layer,
wherein the second electrode, the fourth electrode, and the sixth electrode are provided as a common layer,
wherein the first EL element included in the first pixel which emits red light is configured to emit light by a triplet exciton,
wherein the third EL element included in the third pixel which emits blue light is configured to emit light by a singlet exciton, and
wherein an operation voltage of the first EL element, an operation voltage of the second EL element, and an operation voltage of the third EL element are in a range of 10 V or less.
7. The active matrix type light emitting device according to claim 6 , wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are continuously formed.
8. The active matrix type light emitting device according to claim 6 ,
wherein the first EL element further comprises an electron transporting layer between the first electrode and the second electrode,
wherein the second EL element further comprises an electron transporting layer between the third electrode and the fourth electrode,
wherein the third EL element further comprises an electron transporting layer between the fifth electrode and the sixth electrode, and
wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are provided as a common layer.
9. The active matrix type light emitting device according to claim 8 , wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are continuously formed.
10. The active matrix type light emitting device according to claim 6 , wherein the first electrode, the third electrode, the fifth electrode each comprises an oxide conductive film which transmits visible light.
11. An active matrix type light emitting device comprising a pixel portion comprising:
a first pixel which emits red light comprising:
a first EL element comprising a hole injecting layer and a light emitting layer between a first electrode and a second electrode;
a first current controlling TFT electrically connected to the first electrode, wherein the first current controlling TFT is configured to control a current flowing in the first EL element;
a first switching TFT configured to control a signal to be input to a gate electrode of the first current controlling TFT; and
a first capacitor electrically connected to the gate electrode of the first current controlling TFT, wherein the first capacitor is configured to maintain a voltage applied to the gate electrode of the first current controlling TFT;
a second pixel which emits green light comprising:
a second EL element comprising a hole injecting layer and a light emitting layer between a third electrode and a fourth electrode;
a second current controlling TFT electrically connected to the third electrode, wherein the second current controlling TFT is configured to control a current flowing in the second EL element;
a second switching TFT configured to control a signal to be input to a gate electrode of the second current controlling TFT; and
a second capacitor electrically connected to the gate electrode of the second current controlling TFT, wherein the second capacitor is configured to maintain a voltage applied to the gate electrode of the second current controlling TFT;
a third pixel which emits blue light comprising:
a third EL element comprising a hole injecting layer and a light emitting layer between a fifth electrode and a sixth electrode;
a third current controlling TFT electrically connected to the fifth electrode, wherein the third current controlling TFT is configured to control a current flowing in the third EL element;
a third switching TFT configured to control a signal to be input to a gate electrode of the third current controlling TFT; and
a third capacitor electrically connected to the gate electrode of the third current controlling TFT, wherein the third capacitor is configured to maintain a voltage applied to the gate electrode of the third current controlling TFT;
wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are provided as a common layer,
wherein the second electrode, the fourth electrode, and the sixth electrode are provided as a common layer,
wherein the first EL element included in the first pixel which emits red light is configured to emit light by a triplet exciton, and
wherein the third EL element included in the third pixel which emits blue light is configured to emit light by a singlet exciton.
12. The active matrix type light emitting device according to claim 11 , wherein the first current controlling TFT, the second current controlling TFT, the third current controlling TFT, the first switching TFT, the second switching TFT, and the third switching TFT are each formed of n-channel TFT.
13. The active matrix type light emitting device according to claim 11 , wherein the first current controlling TFT, the second current controlling TFT, the third current controlling TFT, the first switching TFT, the second switching TFT, and the third switching TFT are each formed of p-channel TFT.
14. The active matrix type light emitting device according to claim 11 , wherein an operation voltage of the first EL element, an operation voltage of the second EL element, and an operation voltage of the third EL element are in a range of 10 V or less.
15. The active matrix type light emitting device according to claim 11 , wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are continuously formed.
16. The active matrix type light emitting device according to claim 11 ,
wherein the first EL element further comprises an electron transporting layer between the first electrode and the second electrode,
wherein the second EL element further comprises an electron transporting layer between the third electrode and the fourth electrode,
wherein the third EL element further comprises an electron transporting layer between the fifth electrode and the sixth electrode, and
wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are provided as a common layer.
17. The active matrix type light emitting device according to claim 16 , wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are continuously formed.
18. The active matrix type light emitting device according to claim 11 , wherein the first electrode, the third electrode, the fifth electrode each comprises an oxide conductive film which transmits visible light.
19. An active matrix type light emitting device comprising a pixel portion comprising:
a first pixel which emits red light comprising:
a first EL element comprising a hole injecting layer and a light emitting layer between a first electrode and a second electrode;
a first current controlling TFT electrically connected to the first electrode, wherein the first current controlling TFT is configured to control a current flowing in the first EL element;
a first switching TFT configured to control a signal to be input to a gate electrode of the first current controlling TFT; and
a first capacitor electrically connected to the gate electrode of the first current controlling TFT, wherein the first capacitor is configured to maintain a voltage applied to the gate electrode of the first current controlling TFT;
a second pixel which emits green light comprising:
a second EL element comprising a hole injecting layer and a light emitting layer between a third electrode and a fourth electrode;
a second current controlling TFT electrically connected to the third electrode, wherein the second current controlling TFT is configured to control a current flowing in the second EL element;
a second switching TFT configured to control a signal to be input to a gate electrode of the second current controlling TFT; and
a second capacitor electrically connected to the gate electrode of the second current controlling TFT, wherein the second capacitor is configured to maintain a voltage applied to the gate electrode of the second current controlling TFT;
a third pixel which emits blue light comprising:
a third EL element comprising a hole injecting layer and a light emitting layer between a fifth electrode and a sixth electrode;
a third current controlling TFT electrically connected to the fifth electrode, wherein the third current controlling TFT is configured to control a current flowing in the third EL element;
a third switching TFT configured to control a signal to be input to a gate electrode of the third current controlling TFT; and
a third capacitor electrically connected to the gate electrode of the third current controlling TFT, wherein the third capacitor is configured to maintain a voltage applied to the gate electrode of the third current controlling TFT;
wherein the first current controlling TFT, the second current controlling TFT, the third current controlling TFT, the first switching TFT, the second switching TFT, and the third switching TFT are each formed of p-channel TFT,
wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are provided as a common layer,
wherein the second electrode, the fourth electrode, and the sixth electrode are provided as a common layer,
wherein the first EL element included in the first pixel which emits red light is configured to emit light by a triplet exciton,
wherein the third EL element included in the third pixel which emits blue light is configured to emit light by a singlet exciton, and
wherein an operation voltage of the first EL element, an operation voltage of the second EL element, and an operation voltage of the third EL element are in a range of 10 V or less.
20. The active matrix type light emitting device according to claim 19 , wherein the hole injecting layer included in the first EL element, the hole injecting layer included in the second EL element, and the hole injecting layer included in the third EL element are continuously formed.
21. The active matrix type light emitting device according to claim 19 ,
wherein the first EL element further comprises an electron transporting layer between the first electrode and the second electrode,
wherein the second EL element further comprises an electron transporting layer between the third electrode and the fourth electrode,
wherein the third EL element further comprises an electron transporting layer between the fifth electrode and the sixth electrode, and
wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are provided as a common layer.
22. The active matrix type light emitting device according to claim 21 , wherein the electron transporting layer included in the first EL element, the electron transporting layer included in the second EL element, and the electron transporting layer included in the third EL element are continuously formed.
23. The active matrix type light emitting device according to claim 19 , wherein the first electrode, the third electrode, the fifth electrode each comprises an oxide conductive film which transmits visible light.
24. An active matrix type light emitting device comprising a pixel portion comprising:
a first pixel which emits red light comprising:
a first EL element comprising a hole injecting layer and a first light emitting layer between a first electrode and a second electrode, wherein the first light emitting layer is provided between the second electrode and the hole injecting layer;
a first current controlling TFT electrically connected to the first electrode, wherein the first current controlling TFT is configured to control a current flowing in the first EL element;
a first switching TFT configured to control a signal to be input to a gate electrode of the first current controlling TFT; and
a first capacitor electrically connected to the gate electrode of the first current controlling TFT;
a second pixel which emits blue light comprising:
a second EL element comprising the hole injecting layer and a second light emitting layer between a third electrode and the second electrode, wherein the second light emitting layer is provided between the second electrode and the hole injecting layer;
a second current controlling TFT electrically connected to the third electrode, wherein the second current controlling TFT is configured to control a current flowing in the second EL element;
a second switching TFT configured to control a signal to be input to a gate electrode of the second current controlling TFT; and
a second capacitor electrically connected to the gate electrode of the second current controlling TFT;
wherein the first EL element included in the first pixel which emits red light is configured to emit light by a triplet exciton, and
wherein the second EL element included in the second pixel which emits blue light is configured to emit light by a singlet exciton.
25. The active matrix type light emitting device according to claim 24 , the pixel portion further comprising a third pixel which emits green light comprising:
a third EL element comprising the hole injecting layer and a third light emitting layer between a fourth electrode and the second electrode, wherein the third light emitting layer is provided between the second electrode and the hole injecting layer;
a third current controlling TFT electrically connected to the fourth electrode, wherein the third current controlling TFT is configured to control a current flowing in the third EL element;
a third switching TFT configured to control a signal to be input to a gate electrode of the third current controlling TFT; and
a third capacitor electrically connected to the gate electrode of the third current controlling TFT.
26. The active matrix type light emitting device according to claim 24 , wherein the first current controlling TFT, the second current controlling TFT, the first switching TFT, and the second switching TFT are each formed of n-channel TFT.
27. The active matrix type light emitting device according to claim 24 , wherein the first current controlling TFT, the second current controlling TFT, the first switching TFT, and the second switching TFT are each formed of p-channel TFT.
28. The active matrix type light emitting device according to claim 24 , wherein an operation voltage of the first EL element and an operation voltage of the second EL element are in a range of 10 V or less.
29. The active matrix type light emitting device according to claim 24 , wherein the hole injecting layer extends over the first pixel and the second pixel.
30. The active matrix type light emitting device according to claim 24 ,
wherein the first EL element further comprises an electron transporting layer between the hole injecting layer and the second electrode, and
wherein the second EL element further comprises the electron transporting layer between the hole injecting layer and the second electrode.
31. The active matrix type light emitting device according to claim 30 , wherein the electron transporting layer extends over the first pixel and the second pixel.
32. The active matrix type light emitting device according to claim 24 , wherein the first electrode and the third electrode each comprises an oxide conductive film which transmits visible light.
33. An active matrix type light emitting device comprising a pixel portion comprising:
a first pixel which emits red light comprising:
a first EL element comprising a hole injecting layer and a first light emitting layer between a first electrode and a second electrode, wherein the first light emitting layer is provided between the second electrode and the hole injecting layer;
a first current controlling TFT electrically connected to the first electrode, wherein the first current controlling TFT is configured to control a current flowing in the first EL element;
a first switching TFT configured to control a signal to be input to a gate electrode of the first current controlling TFT; and
a first capacitor electrically connected to the gate electrode of the first current controlling TFT;
a second pixel which emits blue light comprising:
a second EL element comprising the hole injecting layer and a second light emitting layer between a third electrode and the second electrode, wherein the second light emitting layer is provided between the second electrode and the hole injecting layer;
a second current controlling TFT electrically connected to the third electrode, wherein the second current controlling TFT is configured to control a current flowing in the second EL element;
a second switching TFT configured to control a signal to be input to a gate electrode of the second current controlling TFT; and
a second capacitor electrically connected to the gate electrode of the second current controlling TFT;
wherein the first current controlling TFT, the second current controlling TFT, the first switching TFT, and the second switching TFT are each formed of p-channel TFT,
wherein the first EL element included in the first pixel which emits red light is configured to emit light by a triplet exciton,
wherein the second EL element included in the second pixel which emits blue light is configured to emit light by a singlet exciton, and
wherein an operation voltage of the first EL element, and an operation voltage of the second EL element are in a range of 10 V or less.
34. The active matrix type light emitting device according to claim 33 , wherein the hole injecting layer extends over the first pixel and the second pixel.
35. The active matrix type light emitting device according to claim 33 ,
wherein the first EL element further comprises an electron transporting layer between the hole injecting layer and the second electrode, and
wherein the second EL element further comprises the electron transporting layer between the hole injecting layer and the second electrode.
36. The active matrix type light emitting device according to claim 35 , wherein the electron transporting layer extends over the first pixel and the second pixel.
37. The active matrix type light emitting device according to claim 33 , wherein the first electrode and the third electrode each comprises an oxide conductive film which transmits visible light.