Light emitting device and electronic device

• US 20060284204A1
• Filed: 06/05/2006
• Published: 12/21/2006
• Est. Priority Date: 06/09/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Matsubara, Tomoe, Yamazaki, Shunpei
• Granted Patent: US 8,269,227 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask
• CPC Class Codes: H01L 29/78645 with multiple gate
• CPC Class Codes: H10K 2102/3031 Two-side emission, e.g. transparent OLEDs [TOLED]
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/00 Organic light-emitting devices integrated devices or assemblies of multiple devices H10K59/00, H10K65/00; organic semiconductor lasers H01S5/36
• CPC Class Codes: H10K 50/10 OLEDs or polymer light-emitting diodes [PLED]
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• 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 59/876 comprising a resonant cavity structure, e.g. Bragg reflector pair

Abstract

The invention provides a light emitting device which uses a color conversion layer, with high light emission efficiency and a low driving voltage. The light emitting device includes a light emitting element having a pair of electrodes and a layer containing an organic compound sandwiched between the pair of electrodes, and a color conversion layer which absorbs light emitted from the light emitting element and emits light with a longer wavelength than a wavelength of the absorbed light. A portion of the layer containing an organic compound includes a buffer layer containing a composite material including an organic compound having a hole transporting property and a metal compound. The thickness of the buffer layer is determined so that the light emission efficiency becomes high.

Claims

1. A light emitting device comprising:

a light emitting element comprising a pair of electrodes and a layer containing an organic compound sandwiched between the pair of electrodes; and

a color conversion layer which absorbs light emitted from the light emitting element and generates light with a longer wavelength than a wavelength of the absorbed light,

wherein the layer includes a buffer layer containing a composite material comprising an organic compound which has a hole transporting property and a metal compound.

2. The light emitting device according to claim 1, wherein one of the pair of electrodes comprises a material having a reflectivity of 70% or more against light emitted from a light emitting layer, and the other one of the pair of electrodes comprises a transparent conductive material.

3. The light emitting device according to claim 1, wherein the metal compound is oxide or nitride of transition metal.

4. The light emitting device according to claim 1, wherein the metal compound is oxide or nitride of metal which belongs to groups 4 to 8 of a periodic table of elements.

5. The light emitting device according to claim 1, wherein the metal compound is selected from the group consisting of vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, and ruthenium oxide.

6. The light emitting device according to claim 1, wherein a layer which has a function to generate an electron to the buffer layer is provided on a side of a layer which functions as an anode of the buffer layer.

7. The light emitting device according to claim 1, wherein the color conversion layer is formed of a substance which absorbs light in a blue region and emits fluorescence in a red region.

8. The light emitting device according to claim 1, wherein the color conversion layer is formed of a substance which absorbs light in a blue region and emits fluorescence in a green region.

9. The light emitting device according to claim 1, wherein the color conversion layer is provided between a substrate on a side to extract light and the light emitting element.

10. The light emitting device according to claim 1, wherein the color conversion layer is formed to be in contact with one of the pair of electrodes which comprises a transparent conductive material.

11. An electronic device mounting the light emitting device according to claim 1, wherein the electronic device is selected from the group consisting of a camera, a goggle type display, a navigation system, an audio reproducing device, a computer, a game machine, a mobile information terminal, and an image reproducing device.

12. A light emitting device comprising:

a light emitting element comprising a pair of electrodes and a layer containing an organic compound sandwiched between the pair of electrodes; and

a color conversion layer which absorbs light emitted from the light emitting element and generates light with a longer wavelength than a wavelength of the absorbed light,

wherein the layer includes a buffer layer comprising a composite material comprising an organic compound which has a hole transporting property and a metal compound; and

wherein an optical distance L between a light emitting region of the light emitting layer and an electrode where the buffer layer is formed based on the light emitting layer is controlled by a thickness of the buffer layer.

13. The light emitting device according to claim 12, wherein an optical distance L between the light emitting region and the electrode satisfies L=(2m−

1)λ

/4 when the maximum wavelength of light emitted from the light emitting element is λ

.

14. The light emitting device according to claim 12, wherein one of the pair of electrodes comprises a material having a reflectivity of 70% or more against light emitted from a light emitting layer, and the other one of the pair of electrodes comprises a transparent conductive material.

15. The light emitting device according to claim 12, wherein the metal compound is oxide or nitride of transition metal.

16. The light emitting device according to claim 12, wherein the metal compound is oxide or nitride of metal which belongs to groups 4 to 8 of a periodic table of elements.

17. The light emitting device according to claim 12, wherein the metal compound is selected from the group consisting of vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, and ruthenium oxide.

18. The light emitting device according to claim 12, wherein a layer which has a function to generate an electron to the buffer layer is provided on a side of a layer which functions as an anode of the buffer layer.

19. The light emitting device according to claim 12, wherein the color conversion layer is formed of a substance which absorbs light in a blue region and emits fluorescence in a red region.

20. The light emitting device according to claim 12, wherein the color conversion layer is formed of a substance which absorbs light in a blue region and emits fluorescence in a green region.

21. The light emitting device according to claim 12, wherein the color conversion layer is provided between a substrate on a side to extract light and the light emitting element.

22. The light emitting device according to claim 12, wherein the color conversion layer is formed to be in contact with one of the pair of electrodes which comprises a transparent conductive material.

23. An electronic device mounting the light emitting device according to claim 12, wherein the electronic device is selected from the group consisting of a camera, a goggle type display, a navigation system, an audio reproducing device, a computer, a game machine, a mobile information terminal, and an image reproducing device.