Light-Emitting Element, Light-Emitting Device, and Display Device

• US 20120205685A1
• Filed: 02/08/2012
• Published: 08/16/2012
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Satoshi, Sasaki, Toshiki, Ohsawa, Nobuharu, Ushikubo, Takahiro, Yamazaki, Shunpei
• Granted Patent: US 9,000,458 B2
• Time in Patent Office: Days
• US Class Current: 257/89
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 50/131 with spacer layers between the electroluminescent layers
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 50/818 Reflective anodes, e.g. ITO combined with thick metallic layers
• CPC Class Codes: H10K 50/828 Transparent cathodes, e.g. comprising thin metal layers
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 50/856 comprising reflective means
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths

Abstract

A light-emitting element with which a reduction in power consumption and an improvement in productivity of a display device can be achieved is provided. A technique of manufacturing a display device with high productivity is provided. The light-emitting element includes an electrode having a reflective property, and a first light-emitting layer, a charge generation layer, a second light-emitting layer, and an electrode having a light-transmitting property stacked in this order over the electrode having a reflective property. The optical path length between the electrode having a reflective property and the first light-emitting layer is one-quarter of the peak wavelength of the emission spectrum of the first light-emitting layer. The optical path length between the electrode having a reflective property and the second light-emitting layer is three-quarters of the peak wavelength of the emission spectrum of the second light-emitting layer.

Claims

1. A light-emitting element comprising:

an electrode having a reflective property;

a first light-emitting layer over the electrode having a reflective property;

a first charge generation layer over the first light-emitting layer;

a second light-emitting layer over the first charge generation layer; and

an electrode having a light-transmitting property over the second light-emitting layer,

wherein an optical path length between the electrode having a reflective property and the first light-emitting layer is one-quarter of a peak wavelength of an emission spectrum of the first light-emitting layer, and

wherein an optical path length between the electrode having a reflective property and the second light-emitting layer is three-quarters of a peak wavelength of an emission spectrum of the second light-emitting layer.

2. The light-emitting element according to claim 1, wherein colors of light emitted from the first light-emitting layer and the second light-emitting layer are different.

3. The light-emitting element according to claim 1, wherein the light-emitting element emits white light.

4. The light-emitting element according to claim 1, further comprising:

a first substrate provided with the electrode having a reflective property; and

a second substrate over the electrode having a light-transmitting property,

wherein the second substrate is a light-transmitting substrate.

5. The light-emitting element according to claim 1, further comprising:

a second charge generation layer over the second light-emitting layer; and

a third light-emitting layer between the second charge generation layer and the electrode having a light-transmitting property,

wherein an optical path length between the electrode having a reflective property and the third light-emitting layer is five-quarters of a peak wavelength of an emission spectrum of the third light-emitting layer.

6. The light-emitting element according to claim 5, wherein colors of light emitted from the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are different.

7. The light-emitting element according to claim 1, further comprising:

a hole-injection layer between the electrode having a reflective property and the first light-emitting layer; and

a second charge generation layer between the second light-emitting layer and the electrode having a light-transmitting property,

wherein the hole-injection layer comprises a first organic compound and an inorganic compound,

wherein the first charge generation layer comprises the first organic compound and the inorganic compound, and

wherein the second charge generation layer comprises a second organic compound and the inorganic compound.

8. A light-emitting device comprising the light-emitting element according to claim 1.

9. A lighting device comprising the light-emitting element according to claim 1.

10. A light-emitting device comprising:

a first light-emitting element, the first light-emitting element comprising;

an electrode having a reflective property;

a first light-emitting layer over the electrode having a reflective property;

a first charge generation layer over the first light-emitting layer;

a second light-emitting layer over the first charge generation layer; and

an electrode having a light-transmitting property over the second light-emitting layer;

a first color filter layer over the first light-emitting element;

a second light-emitting element adjacent to the first light-emitting element; and

a second color filter layer over the second light-emitting element,

wherein an optical path length between the electrode having a reflective property and the first light-emitting layer is one-quarter of a peak wavelength of an emission spectrum of the first light-emitting layer,

wherein an optical path length between the electrode having a reflective property and the second light-emitting layer is three-quarters of a peak wavelength of an emission spectrum of the second light-emitting layer,

wherein the first color filter layer transmits light with a peak wavelength of the emission spectrum of the first light-emitting layer, and

wherein the second color filter layer transmits light with a peak wavelength of the emission spectrum of the second light-emitting layer.

11. The light-emitting device according to claim 10, wherein colors of light emitted from the first light-emitting layer and the second light-emitting layer are different.

12. The light-emitting device according to claim 10, further comprising:

a first substrate provided with the first light-emitting element and the second light-emitting element; and

a second substrate provided with the first color filter layer and the second color filter layer,

wherein the second substrate is a light-transmitting substrate.

13. The light-emitting device according to claim 10, further comprising:

a hole-injection layer between the electrode having a reflective property and the first light-emitting layer; and

a second charge generation layer between the second light-emitting layer and the electrode having a light-transmitting property,

wherein the hole-injection layer comprises a first organic compound and an inorganic compound,

wherein the first charge generation layer comprises the first organic compound and the inorganic compound, and

wherein the second charge generation layer comprises a second organic compound and the inorganic compound.

14. A light-emitting device according to claim 10, wherein the light-emitting device is a display device.

15. A light-emitting device comprising:

a plurality of light-emitting elements, the plurality of light-emitting elements each comprising;

an electrode having a reflective property;

a first light-emitting layer over the electrode having a reflective property;

a first charge generation layer over the first light-emitting layer;

a second light-emitting layer over the first charge generation layer;

a second charge generation layer over the second light-emitting layer;

a third light-emitting layer over the second charge generation layer;

an electrode having a light-transmitting property over the third light-emitting layer; and

a plurality of color filter layers provided over the plurality of light-emitting elements,

wherein an optical path length between the electrode having a reflective property and the first light-emitting layer is one-quarter of a peak wavelength of an emission spectrum of the first light-emitting layer,

wherein an optical path length between the electrode having a reflective property and the second light-emitting layer is three-quarters of a peak wavelength of an emission spectrum of the second light-emitting layer,

wherein an optical path length between the electrode having a reflective property and the third light-emitting layer is five-quarters of a peak wavelength of an emission spectrum of the third light-emitting layer, and

wherein the plurality of color filter layers comprise at least;

a first color filter layer transmitting light with a peak wavelength of the emission spectrum of the first light-emitting layer;

a second color filter layer transmitting light with a peak wavelength of the emission spectrum of the second light-emitting layer; and

a third color filter layer transmitting light with a peak wavelength of the emission spectrum of the third light-emitting layer.

16. The light-emitting device according to claim 15, wherein colors of light emitted from the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are different.

17. The light-emitting device according to claim 15, further comprising:

a first substrate provided with the plurality of light-emitting elements; and

a second substrate provided with the plurality of color filter layers,

wherein the second substrate is a light-transmitting substrate.

18. A light-emitting device according to claim 15, wherein the light-emitting device is a display device.