Light emitting device

• US 7,601,988 B2
• Filed: 09/22/2005
• Issued: 10/13/2009
• 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:
  US10/577,127
• Publication Number:
  US 20070131948A1
• Time in Patent Office: 1,482 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, 313502-509
• 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 and in contact with 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 a thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element.

3. The light-emitting device according to any one of claims 1 and 2, wherein the thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element so that light-extraction efficiency of light emitted from the light-emitting layer and reflected light, which has been emitted from the light-emitting layer and is reflected on the first electrode, can be increased.

8. The light-emitting device according to any one of claims 1, 2, 6 and 7, wherein the second electrode comprises indium tin oxide including silicon oxide.

22. The light-emitting device according to any one of claims 1, 2, 6, 7, 16, 17, and 18, 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.

24. The light-emitting device according to any one of claims 1, 2, and 6, wherein a thickness of the third layer of the first light-emitting element is different from that of the second light-emitting element.

2. 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 and in contact with 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 first layer is a layer in which an organic compound and a metal oxide are mixed, and

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

4. The light-emitting device according to claim 2, wherein the metal oxide is selected from the group consisting of molybdenum oxide, vanadium oxide and rhenium oxide.

5. The light-emitting device according to claim 2, wherein the organic compound is selected from the group consisting of 4,4′

-bis[N-(1-naphthyl)-N-phenylamino]biphenyl;

4,4′

-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl;

4,4′

,4″

-tris(N,N-diphenylamino)triphenylamine;

4,4′

,4″

-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine;

4,4′

-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl;

phthalocyanine;

copper phthalocyanine; and

vanadyl phthalocyanine.

6. 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 and in contact with 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 a thickness of the first layer of the first light-emitting element is different from that of the second light-emitting element.

7. 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 anon-light-transmitting property;

a first layer serving as a layer generating holes over and in contact with 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 a thickness of the first layer is different depending on each of the emission colors so that light-extraction efficiency of light emitted from the light-emitting layer and reflected light, which has been emitted from the light-emitting layer and is reflected on the first electrode, can be increased.

25. The light-emitting device according to claim 7, wherein a thickness of the third layer is different depending on each of the emission colors so that light-extraction efficiency of light emitted from the light-emitting layer and reflected light, which has been emitted from the light-emitting layer and is reflected on the first electrode, can be increased.

9. A light-emitting device comprising:

a plurality of transistors provided at interconnection portions formed by signal lines and scanning lines;

a plurality of first electrodes that are connected to the plurality of transistors and each has a non-light-transmitting property;

a plurality of first layers serving as layers generating holes over and in contact with the plurality of first electrodes, respectively;

a plurality of second layers serving as layers including any of light-emitting layers emitting first to third light over the plurality of first layers;

a plurality of third layers serving as layers generating electrons over the plurality of second layers; and

a second electrode that has a light transmitting property over the plurality of third layers,

wherein thicknesses of the plurality of first layers are different depending on each light-emitting element emitting the first to third light.

10. A light-emitting device comprising:

a plurality of transistors provided at interconnection portions formed by signal lines and scanning lines;

a plurality of first electrodes that are connected to the plurality of transistors and each has a non-light-transmitting property;

a plurality of first layers serving as layers generating holes over and in contact with the plurality of first electrodes, respectively;

a plurality of second layers serving as layers including at least one of light-emitting layers emitting first to third light over the plurality of first layers;

a plurality of third layers serving as layers generating electrons over the plurality of second layers; and

a second electrode that has a light transmitting property over the plurality of first layers, the plurality of second layers and the plurality of third layers,

wherein the plurality of first layers are each a layer in which an organic compound and a metal oxide are mixed, and

wherein thicknesses of the plurality of first layers are different depending on each light-emitting element emitting the first to third light.

11. The light-emitting device according to claim 10, wherein the metal oxide is selected from the group consisting of molybdenum oxide, vanadium oxide and rhenium oxide.

14. The light-emitting device according to claim 10, wherein the organic compound is selected from the group consisting of 4,4′

-bis[N-(1-naphthyl)-N-phenylamino]biphenyl;

4,4′

-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl;

4,4′

,4″

-tris(N,N-diphenylamino)triphenylamine;

4,4′

,4″

-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine;

4,4′

-bis{N-[4-(N,N-di-m-tolylamino)phenyl]-N-phenylamino}biphenyl;

phthalocyanine;

copper phthalocyanine; and

vanadyl phthalocyanine.

15. The light-emitting device according to any one of claims 9, 10 and 12, wherein the second electrode comprises indium tin oxide including silicon oxide.

23. The light-emitting device according to any one of claims 9, 10, and 12, wherein an optical distance between one of light-emitting layers emitting first to third light and one of the plurality of first electrodes is (2m−

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

26. The light-emitting device according to any one of claims 9, 10, and 12, wherein a thickness of the plurality of third layers are different depending on each light-emitting element emitting the first to third light.

12. A light-emitting device comprising:

a plurality of transistors provided at interconnection portions formed by signal lines and scanning lines;

a plurality of first electrodes that are connected to the plurality of transistors and each has a non-light-transmitting property;

a plurality of first layers serving as layers generating holes over and in contact with the plurality of first electrodes, respectively;

a plurality of second layers serving as layers including at least one of light-emitting layers emitting first to third light over the plurality of first layers;

a plurality of third layers serving as layers generating electrons over the plurality of second layers;

a plurality of fourth layers serving as layers generating holes over the plurality of third layers; and

a second electrode that has a light transmitting property over the plurality of fourth layers,

wherein thicknesses of the plurality of first layers are different depending on each light-emitting element emitting the first to third light.

13. The light-emitting device according to claim 12, wherein thicknesses of the plurality of first layers are different depending on each light-emitting element emitting the first to third light so that light-extraction efficiency of light emitted from the light-emitting layer and reflected light, which has been emitted from the light-emitting layer and is reflected on the first electrode, can be increased.

16. A light-emitting device comprising:

a plurality of types of color filters having different optical characteristics;

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

a first layer over and in contact with the first electrode;

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

a third layer over the second layer; and

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

wherein any of the first to third layers has an organic material and a metal oxide, and

wherein a thickness of the first layer is different depending on each of the optical characteristics.

19. The light-emitting device according to any one of claims 16, 17 and 18, wherein the plurality of types of color filters are formed on an emission side.

20. The light-emitting device according to any one of claims 16, 17 and 18, wherein the metal oxide is selected from the group consisting of molybdenum oxide, vanadium oxide and rhenium oxide.

21. The light-emitting device according to any one of claims 16, 17 and 18, wherein the second electrode comprises indium tin oxide including silicon oxide.

27. The light-emitting device according to any one of claims 16, 17, and 18, wherein a thickness of the third layer is different depending on each of the optical characteristics.

17. A light-emitting device comprising:

a plurality of types of color filters having different optical characteristics;

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

a first layer serving as a layer generating holes over and in contact with 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 first layer has an organic material and a metal oxide, and

wherein a thickness of the first layer is different depending on each of the optical characteristics.

18. A light-emitting device comprising:

a semiconductor film;

a first electrode that has a non-light-transmitting property formed over the semiconductor film;

a first layer serving as a layer generating holes over and in contact with 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; and

a plurality of types of color filters having different optical characteristics, which are each formed on the second electrode side,

wherein the first layer has an organic material and a metal oxide, and

wherein a thickness of the first layer is different depending on each of the optical characteristics.