Light Emitting Device

• US 20080169751A1
• Filed: 03/17/2008
• Published: 07/17/2008
• 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 7,915,808 B2
• Time in Patent Office: Days
• US Class Current: 313/499
• 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 first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises an EL element,

wherein the EL element of the first pixel comprises a triplet compound, and

wherein the EL element of the second pixel comprises a singlet compound.

2. A light emitting device according to claim 1, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

3. A light emitting device according to claim 1, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

4. A light emitting device according to claim 1, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.

5. A light emitting device comprising:

a first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises a first thin film transistor, a second thin film transistor electrically connected to the first thin film transistor, and an EL element electrically connected to the second thin film transistor, and

wherein the EL element of the first pixel comprises a triplet compound, and

wherein the EL element of the second pixel comprises a singlet compound.

6. A light emitting device according to claim 5, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

7. A light emitting device according to claim 5, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

8. A light emitting device according to claim 5, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.

9. A light emitting device comprising:

a first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises a first thin film transistor, a second thin film transistor electrically connected to the first thin film transistor, and an EL element electrically connected to the second thin film transistor, and

wherein the EL element of the first pixel comprises a triplet compound,

wherein the EL element of the second pixel comprises a singlet compound,

wherein the first thin film transistor is an n-channel thin film transistor, and

wherein the second thin film transistor is an n-channel thin film transistor.

10. A light emitting device according to claim 9, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

11. A light emitting device according to claim 9, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

12. A light emitting device according to claim 9, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.

13. A light emitting device comprising:

a first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises a first thin film transistor, a second thin film transistor electrically connected to the first thin film transistor, and an EL element electrically connected to the second thin film transistor, and

wherein the EL element of the first pixel comprises a triplet compound,

wherein the EL element of the second pixel comprises a singlet compound,

wherein the first thin film transistor is a p-channel thin film transistor, and

wherein the second thin film transistor is a p-channel thin film transistor.

14. A light emitting device according to claim 13, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

15. A light emitting device according to claim 13, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

16. A light emitting device according to claim 13, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.

17. A light emitting device comprising:

a first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises a first thin film transistor, a second thin film transistor electrically connected to the first thin film transistor, and an EL element electrically connected to the second thin film transistor, and

wherein the EL element of the first pixel comprises a triplet compound,

wherein the EL element of the second pixel comprises a singlet compound,

wherein the first thin film transistor is an n-channel thin film transistor, and

wherein the second thin film transistor is a p-channel thin film transistor.

18. A light emitting device according to claim 17, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

19. A light emitting device according to claim 17, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

20. A light emitting device according to claim 17, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.

21. A light emitting device comprising:

a first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises a first thin film transistor, a second thin film transistor electrically connected to the first thin film transistor, and an EL element electrically connected to the second thin film transistor, and

wherein the EL element of the first pixel comprises a triplet compound,

wherein the EL element of the second pixel comprises a singlet compound,

wherein the first thin film transistor is a p-channel thin film transistor, and

wherein the second thin film transistor is an n-channel thin film transistor.

22. A light emitting device according to claim 21, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

23. A light emitting device according to claim 21, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

24. A light emitting device according to claim 21, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.

25. A light emitting device comprising:

a first pixel for emitting a first light; and

a second pixel for emitting a second light,

wherein each of the first light and the second light has a different color,

wherein each of the first pixel and the second pixel comprises an EL element,

wherein the EL element of the first pixel comprises a first light emitting layer including a triplet compound and a carrier injecting layer adjacent to the first light emitting layer, and

wherein the EL element of the second pixel comprises a second light emitting layer including a singlet compound and the carrier injecting layer adjacent to the second light emitting layer.

26. A light emitting device according to claim 25, wherein the carrier injecting layer is a hole injecting layer.

27. A light emitting device according to claim 25, wherein the carrier injecting layer is an electron injecting layer.

28. A light emitting device according to claim 25, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the first electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the first electrode.

29. A light emitting device according to claim 25, wherein the EL element of each of the first pixel and the second pixel comprises a first electrode over a substrate, a light emitting layer over the first electrode and a second electrode over the light emitting layer, and wherein the second electrode has a light transmitting property so as to allow light emitted by the EL element to exit the light emitting device through the second electrode.

30. A light emitting device according to claim 25, wherein the EL element of each of the first pixel and the second pixel is operated in a range of 10V or less.