Light emitting device having singlet and triplet compounds with different emission colors

• US 8,304,985 B2
• Filed: 03/11/2011
• Issued: 11/06/2012
• Est. Priority Date: 06/05/2000
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Guharay, Karabi
• Application Number:
  US13/045,614
• Publication Number:
  US 20110156580A1
• Time in Patent Office: 606 Days
• Field of Search: 313/504, 313/506, 428/690
• US Class Current: 313/504
• 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 light emitting layer;

a second light emitting layer;

a third light emitting layer; and

an electrode over the first light emitting layer, the second light emitting layer and the third light emitting layer,

wherein at least one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a singlet compound,

wherein at least the other one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a triplet compound, and

wherein colors of light emitted from the first light emitting layer, the second light emitting layer and the third light emitting layer are different from each other.

2. The light emitting device according to claim 1, wherein the first light emitting layer, the second light emitting layer and the third light emitting layer are not overlapped with each other.

3. The light emitting device according to claim 1, wherein the electrode has a light transmitting property.

4. A light emitting device comprising:

a first electrode;

a first carrier injecting layer over the first electrode;

a first light emitting layer over the first carrier injecting layer;

a second light emitting layer over the first carrier injecting layer;

a third light emitting layer over the first carrier injecting layer;

a second carrier injecting layer over the first light emitting layer, the second light emitting layer and the third light emitting layer; and

a second electrode over the second carrier injecting layer,

wherein at least one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a singlet compound,

wherein at least the other one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a triplet compound, and

wherein colors of light emitted from the first light emitting layer, the second light emitting layer and the third light emitting layer are different from each other.

5. The light emitting device according to claim 4, wherein the first light emitting layer, the second light emitting layer and the third light emitting layer are not overlapped with each other.

6. The light emitting device according to claim 4, wherein the first electrode has a light transmitting property.

7. The light emitting device according to claim 4, wherein the second electrode has a light transmitting property.

8. The light emitting device according to claim 4, wherein the first carrier injecting layer is one of a hole injecting layer and an electron injecting layer.

9. The light emitting device according to claim 8, wherein the second carrier injecting layer is the other of the hole injecting layer and the electron injecting layer.

10. A light emitting device comprising:

a transistor;

an insulating film over the transistor;

a first electrode over the insulating film, the first electrode electrically connected to the transistor;

a first light emitting layer over the first electrode;

a second light emitting layer over the insulating film;

a third light emitting layer over the insulating film; and

a second electrode over the first light emitting layer, the second light emitting layer and the third light emitting layer,

wherein at least one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a singlet compound,

wherein at least the other one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a triplet compound, and

wherein colors of light emitted from the first light emitting layer, the second light emitting layer and the third light emitting layer are different from each other.

11. The light emitting device according to claim 10, wherein the first light emitting layer, the second light emitting layer and the third light emitting layer are not overlapped with each other.

12. The light emitting device according to claim 10, wherein the first electrode has a light transmitting property.

13. The light emitting device according to claim 10, wherein the second electrode has a light transmitting property.

14. The light emitting device according to claim 10, further comprising a second transistor and a third transistor,

wherein the second light emitting layer is located over the second transistor;

and

wherein the third light emitting layer is located over the third transistor.

15. A light emitting device comprising:

a transistor;

an insulating film over the transistor;

a first electrode over the insulating film, the first electrode electrically connected to the transistor;

a first carrier injecting layer over the first electrode;

a first light emitting layer over the first carrier injecting layer;

a second light emitting layer over the first carrier injecting layer;

a third light emitting layer over the first carrier injecting layer;

a second carrier injecting layer over the first light emitting layer, the second light emitting layer and the third light emitting layer; and

a second electrode over the second carrier injecting layer,

wherein at least one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a singlet compound,

wherein at least the other one of the first light emitting layer, the second light emitting layer and the third light emitting layer comprises a triplet compound, and

wherein colors of light emitted from the first light emitting layer, the second light emitting layer and the third light emitting layer are different from each other.

16. The light emitting device according to claim 15, wherein the first light emitting layer, the second light emitting layer and the third light emitting layer are not overlapped with each other.

17. The light emitting device according to claim 15, wherein the first electrode has a light transmitting property.

18. The light emitting device according to claim 15, wherein the second electrode has a light transmitting property.

19. The light emitting device according to claim 15, wherein the first carrier injecting layer is one of a hole injecting layer and an electron injecting layer.

20. The light emitting device according to claim 19, wherein the second carrier injecting layer is the other of the hole injecting layer and the electron injecting layer.