Light emitting device

• US 7,875,893 B2
• Filed: 09/22/2009
• Issued: 01/25/2011
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Satoshi, Kumaki, Daisuke, Ikeda, Hisao, Sakata, Junichiro
• Primary Examiner(s): Smith; Zandra
• Assistant Examiner(s): Patton; Paul E
• Application Number:
  US12/564,233
• Publication Number:
  US 20100006872A1
• Time in Patent Office: 490 Days
• Field of Search: 257 88- 98, 257101-103, 257/79, 257/E51.018, 257/E51.019, 257/E51.022, 257E51026-E51029, 257E5103-E51052, 257E33002-E33004, 438/29, 438/34, 438/35, 438/46, 438/47
• US Class Current: 257/88
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H10K 2102/3026 Top emission
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/17 Carrier injection layers
• CPC Class Codes: H10K 50/171 Electron injection layers
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]
• CPC Class Codes: H10K 85/324 comprising aluminium, e.g. Alq3
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons
• CPC Class Codes: Y02E 10/549 Organic PV cells

Abstract

Light-emitting elements have a problem that their light-extraction efficiency is low due to scattered light or reflected light inside the light-emitting elements. The light-extraction efficiency of the light-emitting elements needs to be enhanced by a new method. According to the present invention, a light-emitting element includes a first layer generating holes, a second layer including a light-emitting layer for each emission color and a third layer generating electrons between an anode and a cathode, and the thickness of the first layer is different depending on each layer including the light-emitting layer for each emission color. A layer in which an organic compound and a metal oxide are mixed is used as the first layer, and thus, the driving voltage is not increased even when the thickness is increased, which is preferable.

Claims

1. A light-emitting device having at least first and second light-emitting elements exhibiting different emission colors, each of the first and second light-emitting elements comprising:

a first electrode that has a non-light-transmitting property;

a first layer serving as a layer generating holes over the first electrode;

a second layer serving as a layer including a light-emitting layer over the first layer;

a third layer serving as a layer generating electrons over the second layer; and

a second electrode that has a light transmitting property over the third layer,

wherein the layer including the light-emitting layer comprises an organic material,

wherein the second electrode comprises a semi-transparent metal material,

wherein a thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element, and

wherein a thickness of the third layer of the first light-emitting element is different from that of the second light-emitting element.

2. The light-emitting device according to claim 1, wherein the first electrode is electrically connected to a transistor provided at interconnection portion formed by a signal line and a scanning line.

3. The light-emitting device according to claim 1, further comprising a plurality of types of color filters having different optical characteristics, which are each formed on the second electrode side.

4. The light-emitting device according to claim 1, wherein the second electrode comprises indium tin oxide including silicon oxide.

5. The light-emitting device according to claim 1, wherein an optical distance between the light-emitting layer and the first electrode is (2m−

1)/4-fold (m is a given positive integer) of an emission wavelength.

6. The light-emitting device according to claim 1, wherein the light-emitting device is incorporated in an electronic device selected from the group consisting of a television set, cameras, a portable information terminal, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.

7. The light-emitting device according to claim 1,

wherein the first light light-emitting element generates blue light,

wherein the second light-emitting element generates red light, and

wherein the thickness of the first light-emitting element is thicker than the second light-emitting element.

8. A light-emitting device having at least first and second light-emitting elements exhibiting different emission colors, each of the first and second light-emitting elements comprising:

a first electrode that has a non-light-transmitting property;

a first layer serving as a layer generating holes over the first electrode;

a second layer serving as a layer including a light-emitting layer over the first layer;

a third layer serving as a layer generating electrons over the second layer;

a fourth layer serving as a layer generating holes over the third layer; and

a second electrode that has a light transmitting property over the fourth layer,

wherein the layer including the light-emitting layer comprises an organic material,

wherein the second electrode comprises a semi-transparent metal material,

wherein a thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element, and

wherein a thickness of the third layer of the first light-emitting element is different from that of the second light-emitting element.

9. The light-emitting device according to claim 8, wherein the first electrode is electrically connected to a transistor provided at interconnection portion formed by a signal line and a scanning line.

10. The light-emitting device according to claim 8, further comprising a plurality of types of color filters having different optical characteristics, which are each formed on the second electrode side.

11. The light-emitting device according to claim 8, wherein the second electrode comprises indium tin oxide including silicon oxide.

12. The light-emitting device according to claim 8, wherein an optical distance between the light-emitting layer and the first electrode is (2m−

1)/4-fold (m is a given positive integer) of an emission wavelength.

13. The light-emitting device according to claim 8, wherein the light-emitting device is incorporated in an electronic device selected from the group consisting of a television set, cameras, a portable information terminal, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.

14. The light-emitting device according to claim 8,

wherein the first light light-emitting element generates blue light,

wherein the second light-emitting element generates red light, and

wherein the thickness of the first light-emitting element is thicker than the second light-emitting element.

15. A light-emitting device having at least first and second light-emitting elements exhibiting different emission colors, each of the first and second light-emitting elements comprising:

a first electrode that has a non-light-transmitting property;

a first layer serving as a layer generating holes over the first electrode;

a second layer serving as a layer including a light-emitting layer over the first layer;

a third layer serving as a layer generating electrons over the second layer; and

a second electrode that has a light transmitting property over the third layer,

wherein the layer including the light-emitting layer comprises an organic material,

wherein the second electrode comprises a semi-transparent metal material,

wherein a thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element,

wherein a thickness of the third layer of the first light-emitting element is different from that of the second light-emitting element,

wherein the first layer is a layer in which an organic compound and a metal oxide are mixed, and

wherein the metal oxide is selected from the group consisting of molybdenum oxide, vanadium oxide and rhenium oxide.

16. The light-emitting device according to claim 15, wherein the first electrode is electrically connected to a transistor provided at interconnection portion formed by a signal line and a scanning line.

17. The light-emitting device according to claim 15, further comprising a plurality of types of color filters having different optical characteristics, which are each formed on the second electrode side.

18. The light-emitting device according to claim 15, wherein the second electrode comprises indium tin oxide including silicon oxide.

19. The light-emitting device according to claim 15, wherein an optical distance between the light-emitting layer and the first electrode is (2m−

1)/4-fold (m is a given positive integer) of an emission wavelength.

20. The light-emitting device according to claim 15, wherein the light-emitting device is incorporated in an electronic device selected from the group consisting of a television set, cameras, a portable information terminal, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.

21. The light-emitting device according to claim 15,

wherein the first light-emitting element generates blue light,

wherein the second light-emitting element generates red light, and

wherein the thickness of the first light-emitting element is thicker than the second light-emitting element.

22. A light-emitting device having at least first and second light-emitting elements exhibiting different emission colors, each of the first and second light-emitting elements comprising:

a first electrode that has a non-light-transmitting property;

a first layer serving as a layer generating holes over the first electrode;

a second layer serving as a layer including a light-emitting layer over the first layer;

a third layer serving as a layer generating electrons over the second layer;

a fourth layer serving as a layer generating holes over the third layer; and

a second electrode that has a light transmitting property over the fourth layer,

wherein the layer including the light-emitting layer comprises an organic material,

wherein the second electrode comprises a semi-transparent metal material,

wherein a thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element,

wherein a thickness of the third layer of the first light-emitting element is different from that of the second light-emitting element,

wherein the first layer is a layer in which an organic compound and a metal oxide are mixed, and

wherein the metal oxide is selected from the group consisting of molybdenum oxide, vanadium oxide and rhenium oxide.

23. The light-emitting device according to claim 22, wherein the first electrode is electrically connected to a transistor provided at interconnection portion formed by a signal line and a scanning line.

24. The light-emitting device according to claim 22, further comprising a plurality of types of color filters having different optical characteristics, which are each formed on the second electrode side.

25. The light-emitting device according to claim 22, wherein the second electrode comprises indium tin oxide including silicon oxide.

26. The light-emitting device according to claim 22, wherein an optical distance between the light-emitting layer and the first electrode is (2m−

1)/4-fold (m is a given positive integer) of an emission wavelength.

27. The light-emitting device according to claim 22, wherein the light-emitting device is incorporated in an electronic device selected from the group consisting of a television set, cameras, a portable information terminal, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.

28. The light-emitting device according to claim 22,

wherein the first light light-emitting element generates blue light,

wherein the second light-emitting element generates red light, and

wherein the thickness of the first light-emitting element is thicker than the second light-emitting element.