Light emitting device
View Patent ↗It is an object of the invention to provide a light emitting device which can display a superior image in which luminescent color from each light emitting layer is beautifully displayed and power consumption is lowered in a light emitting element in which light emitting layers are stacked. One feature of the invention is that, in a light emitting element which comprises light emitting layers stacked between electrodes, each distance between each light emitting layer and an electrode is approximately oddly multiplied ¼ wavelength by controlling a thickness of a layer provided therebetween to enhance luminous output efficiency. Another feature of the invention is that a drive voltage is lowered using a high conductive material for the layer compared with a conventional element.
1. A light-emitting device comprising:
a first substrate;
an anode over the first substrate;
a first mixed layer over and in contact with the anode, the first mixed layer comprising an organic compound and a metal oxide which exhibits an electron accepting property to the organic compound;
a first light-emitting layer over the first mixed layer;
a second mixed layer over the first light-emitting layer, the second mixed layer comprising the organic compound and the metal oxide;
a second light-emitting layer over the second mixed layer;
a layer over the second light-emitting layer, the layer comprising an electron transporting material and a material which exhibits an electron donating property to the electron transporting material;
a cathode over and in contact with the layer;
a color filter over the cathode; and
a second substrate over the color filter,
wherein the first light-emitting layer and the second light-emitting layer are different in emission color from each other,
wherein the anode is a reflective electrode.
2. The light-emitting device according to claim 1 , wherein the anode comprises aluminum.
3. The light-emitting device according to claim 1 , wherein the cathode comprises indium tin oxide.
4. The light-emitting device according to claim 1 , wherein the metal oxide is molybdenum oxide.
5. The light-emitting device according to claim 1 ,
wherein the first light-emitting layer comprises a first organic compound, and
wherein the second light-emitting layer comprises a second organic compound which is different from the first organic compound.
6. The light-emitting device according to claim 1 , wherein the color filter is in contact with the second substrate.
7. The light-emitting device according to claim 1 , wherein the second substrate is selected from a glass substrate, a plastic substrate, and a metal substrate.
8. The light-emitting device according to claim 1 , wherein a thickness of the first mixed layer is arranged so that an optical distance from the first light-emitting layer to the anode is odd multiples of quarter wavelength of emission color of the first light-emitting layer with a range of plus or minus 10% thereof.
9. The light-emitting device according to claim 1 , wherein the light-emitting device emits white light.
10. An electronic device comprising the light-emitting device according to claim 1 , wherein the electronic device is selected from a television receiver, a camera, a mobile phone set, a portable information terminal, a portable game machine, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.
11. A light-emitting device comprising:
a first substrate;
a first light-emitting element, a second light-emitting element, and a third light-emitting element over the first substrate, each of the first light-emitting element, the second light-emitting element, and the third light-emitting element comprising:
an anode over the first substrate;
a first mixed layer over and in contact with the anode, the first mixed layer comprising an organic compound and a metal oxide which exhibits an electron accepting property to the organic compound;
a first light-emitting layer over the first mixed layer;
a second mixed layer over the first light-emitting layer, the second mixed layer comprising the organic compound and the metal oxide;
a second light-emitting layer over the second mixed layer;
a layer over the second light-emitting layer, the layer comprising an electron transporting material and a material which exhibits an electron donating property to the electron transporting material; and
a cathode over and in contact with the layer;
a red color filter over the first light-emitting element;
a green color filter over the second light-emitting element;
a blue color filter over the third light-emitting element; and
a second substrate over the red color filter, the green color filter, and the blue color filter,
wherein the first light-emitting layer and the second light-emitting layer are different in emission color from each other,
wherein the anode is a reflective electrode.
12. The light-emitting device according to claim 11 , wherein the anode comprises aluminum.
13. The light-emitting device according to claim 11 , wherein the cathode comprises indium tin oxide.
14. The light-emitting device according to claim 11 , wherein the metal oxide is molybdenum oxide.
15. The light-emitting device according to claim 11 ,
wherein the first light-emitting layer comprises a first organic compound, and
wherein the second light-emitting layer comprises a second organic compound which is different from the first organic compound.
16. The light-emitting device according to claim 11 , wherein the red color filter, the green color filter, and the blue color filter each are in contact with the second substrate.
17. The light-emitting device according to claim 11 , wherein the second substrate is selected from a glass substrate, a plastic substrate, and a metal substrate.
18. The light-emitting device according to claim 11 , wherein a thickness of the first mixed layer is arranged so that an optical distance from the first light-emitting layer to the anode is odd multiples of quarter wavelength of emission color emitted from the first light-emitting layer with a range of plus or minus 10% thereof.
19. The light-emitting device according to claim 11 , wherein each of the first light-emitting element, the second light-emitting element, and the third light-emitting element emits white light.
20. An electronic device comprising the light-emitting device according to claim 11 , wherein the electronic device is selected from a television receiver, a camera, a mobile phone set, a portable information terminal, a portable game machine, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.
21. The light-emitting device according to claim 1 , wherein a thickness of the first mixed layer is different from a thickness of the second mixed layer.
22. The light-emitting device according to claim 11 , wherein a thickness of the first mixed layer is different from a thickness of the second mixed layer.
23. A light-emitting device comprising:
an anode;
a first mixed layer over and in contact with the anode, the first mixed layer comprising an organic compound and a metal oxide which exhibits an electron accepting property to the organic compound;
a first light-emitting layer over the first mixed layer, the first light-emitting layer comprising a first light-emitting material;
a second mixed layer over the first light-emitting layer, the second mixed layer comprising the organic compound and the metal oxide;
a second light-emitting layer comprising over the second mixed layer, the second light-emitting layer comprising a second light-emitting material;
a layer over the second light-emitting layer, the layer comprising an electron transporting material and a material which exhibits an electron donating property to the electron transporting material; and
a cathode over and in contact with the layer,
wherein the anode is a reflective electrode.
24. The light-emitting device according to claim 23 , wherein the anode comprises aluminum.
25. The light-emitting device according to claim 23 , wherein the cathode comprises indium tin oxide.
26. The light-emitting device according to claim 23 , wherein the metal oxide is molybdenum oxide.
27. The light-emitting device according to claim 23 ,
wherein the first light-emitting layer comprises a first organic compound, and
wherein the second light-emitting layer comprises a second organic compound which is different from the first organic compound.
28. The light-emitting device according to claim 23 , wherein a thickness of the first mixed layer is arranged so that an optical distance from the first light-emitting layer to the anode is odd multiples of quarter wavelength of emission color of the first light-emitting layer with a range of plus or minus 10% thereof.
29. The light-emitting device according to claim 23 , wherein the light-emitting device emits white light.
30. An electronic device comprising the light-emitting device according to claim 23 , wherein the electronic device is selected from a television receiver, a camera, a mobile phone set, a portable information terminal, a portable game machine, a monitor for a computer, a computer, a sound reproducing device, and an image reproducing device.