Light Emitting Device

• US 20070034881A1
• Filed: 04/27/2006
• Published: 02/15/2007
• Est. Priority Date: 04/05/2002
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kuwabara, Hideaki, Yamazaki, Shunpei
• Granted Patent: US 7,692,380 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H10K 50/87 Arrangements for heating or cooling
• CPC Class Codes: H10K 59/8794 Arrangements for heating and cooling
• CPC Class Codes: H10K 85/146 poly N-vinylcarbazol; Derivatives thereof
• CPC Class Codes: H10K 85/60 Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• CPC Class Codes: H10K 85/649 Aromatic compounds comprising a hetero atom
• CPC Class Codes: H10K 85/6565 Oxadiazole compounds

Abstract

When a light emitting element is actuated to allow the light emission, the generation of Joule heat occurs, leading to the decomposition or crystallization of an organic compound to cause the degradation of the light emitting device. Therefore, a light emitting element of the present invention is provided for effecting removing or decreasing the generation of heat. In the present invention, between two electrodes, layers having organic compounds and carbon-based thin films are alternatively laminated one after another for stepping down the driving voltage in the light emitting element using the tunnel effect. In addition, a carbon-based thin film is placed on a film containing an organic compound, so that it prevents the electric filed from being locally concentrated and also prevents the generation of short-circuit between the anode and the cathode.

Claims

1. A light emitting device comprising

a first electrode;

a first light emitting layer formed over the first electrode;

a first barrier layer formed over the first light emitting layer;

a second light emitting layer formed over the first barrier layer;

a second barrier layer formed over the second light emitting layer;

a third light emitting layer formed over the second barrier layer;

a second electrode formed over the third light emitting layer; and

wherein the first barrier layer is an insulating film, and

wherein an electron passes through the first barrier layer by applying a voltage between the first electrode and the second electrode.

2. A light emitting device according to claim 1, wherein the second barrier layer is an insulating film, and

wherein a hole passes through the second barrier layer by applying a voltage between the first electrode and the second electrode, and

wherein the electron and the hole are converted to photons.

3. A light emitting device according to claim 1, wherein each of the first and second barrier layers is a potential barrier.

4. A light emitting device according to claim 1, further comprising a third barrier layer formed between the third light emitting layer and the second electrode.

5. A light emitting device according to claim 1, further comprising a third barrier layer formed between the first light emitting layer and the first electrode.

6. A light emitting device according to claim 1, wherein the light emitting device is a passive matrix electroluminescence display device.

7. A light emitting device according to claim 1, wherein each of the first, second, third light emitting layers includes an organic material.

8. A light emitting device according to claim 1, wherein each of the first and second barrier layers is either transparent or translucent to visible light.

9. An electronic device having the light emitting device according to claim 1, wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggles-type display, a car navigation system, a personal computer, a DVD player, an electronic game machine, or a portable information terminal.

10. A light emitting device comprising:

a first electrode;

a hole transfer layer formed over the first electrode;

light emitting layers formed over the hole transfer layer;

an electron transport layer formed over the light emitting layers; and

a second electrode formed over the electron transport layer,

wherein energy barriers exist between the electron transport layer and the hole transfer layer, and

wherein each of the energy barriers is an insulating film.

11. A light emitting device according to claim 10, wherein an electron injected from the second electrode and a hole injected from the first electrode are converted to photons between the energy barriers.

12. A light emitting device according to claim 10, wherein each of the energy barriers is a barrier film, and wherein the barrier film protects each of the light emitting layers by preventing their materials from being mixed together under the generation of heat at the time of actuating the light emitting device.

13. A light emitting device according to claim 10, wherein the light emitting device is a passive matrix electroluminescence display device.

14. A light emitting device according to claim 10, wherein each of the light emitting layers includes an organic material.

15. An electronic device having the light emitting device according to claim 10, wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggles-type display, a car navigation system, a personal computer, a DVD player, an electronic game machine, or a portable information terminal.

16. A light emitting device comprising:

a first electrode;

a hole transfer layer formed over the first electrode;

a first barrier layer formed over the hole transfer layer;

light emitting layers formed over the first barrier layer;

a second barrier layer formed over the light emitting layers;

an electron transport layer formed over the second barrier layer; and

a second electrode formed over the electron transport layer,

wherein the first barrier layer is an insulating film,

wherein the second barrier layer is an insulating film,

wherein an electron passes through the first barrier layer by applying a voltage between the first electrode and the second electrode, and

wherein the second barrier layer is blocking the electron passed through the first barrier layer.

17. A light emitting device according to claim 16, wherein a hole passes through the second barrier layer by applying a voltage between the first electrode and the second electrode, and

wherein the first barrier layer is blocking the hole passed through the first barrier layer.

18. A light emitting device according to claim 16, wherein the light emitting device is a passive matrix electroluminescence display device.

19. A light emitting device according to claim 16, wherein each of the light emitting layers includes an organic material.

20. An electronic device having the light emitting device according to claim 16, wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggles-type display, a car navigation system, a personal computer, a DVD player, an electronic game machine, or a portable information terminal.

21. A light emitting device including a light emitting element and a thin film transistor electrically connected to the light emitting element, wherein the light emitting element comprises:

a first electrode;

a first light emitting layer formed over the first electrode;

a first barrier layer formed over the first light emitting layer;

a second light emitting layer formed over the first barrier layer;

a second barrier layer formed over the second light emitting layer;

a third light emitting layer formed over the second barrier layer; and

a second electrode formed over the third light emitting layer,

wherein the first barrier layer is an insulating film, and

wherein an electron passes through the first barrier layer by applying a voltage between the first electrode and the second electrode.

22. A light emitting device according to claim 21, wherein the second barrier layer is an insulating film, and

wherein a hole passes through the second barrier layer by applying a voltage between the first electrode and the second electrode, and

wherein the electron and the hole are converted to photons.

23. A light emitting device according to claim 21, wherein each of the first and second barrier layers is a potential barrier.

24. A light emitting device according to claim 21, further comprising a third barrier layer formed between the third light emitting layer and the second electrode.

25. A light emitting device according to claim 21, further comprising a third barrier layer formed between the first light emitting layer and the first electrode.

26. A light emitting device according to claim 21, wherein each of the first, second, and third light emitting layers includes an organic material.

27. A light emitting device according to claim 21, wherein each of the first and second barrier layers is either transparent or translucent to visible light.

28. An electronic device having the light emitting device according to claim 21, wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggles-type display, a car navigation system, a personal computer, a DVD player, an electronic game machine, or a portable information terminal.

29. A light emitting device including a light emitting element and a thin film transistor electrically connected to the light emitting element, wherein the light emitting element comprises:

a first electrode;

a hole transfer layer formed over the first electrode;

light emitting layers formed over the hole transfer layer;

an electron transport layer formed over the light emitting layers; and

a second electrode formed over the electron transport layer,

wherein energy barriers exist between the electron transport layer and the hole transfer layer, and

wherein each of the energy barriers is an insulating film.

30. A light emitting device according to claim 29, wherein an electron injected from the second electrode and a hole injected from the first electrode are converted to photons between the energy barriers.

31. A light emitting device according to claim 29, wherein each of the energy barriers is a barrier film, and wherein the barrier film protects each of the light emitting layers by preventing their materials from being mixed together under the generation of heat at the time of actuating the light emitting device.

32. A light emitting device according to claim 29, wherein each of the light emitting layers includes an organic material.

33. An electronic device having the light emitting device according to claim 29, wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggles-type display, a car navigation system, a personal computer, a DVD player, an electronic game machine, or a portable information terminal.

34. A light emitting device including a light emitting element and a thin film transistor electrically connected to the light emitting element, wherein the light emitting element comprises:

a first electrode;

a hole transfer layer formed over the first electrode;

a first barrier layer formed over the hole transfer layer;

light emitting layers formed over the first barrier layer;

a second barrier layer formed over the light emitting layers;

an electron transport layer formed over the second barrier layer; and

a second electrode formed over the electron transport layer,

wherein the first barrier layer is an insulating film,

wherein the second barrier layer is an insulating film,

wherein an electron passes through the first barrier layer by applying a voltage between the first electrode and the second electrode, and

wherein the second barrier layer is blocking the electron passed through the first barrier layer.

35. A light emitting device according to claim 34, wherein a hole passes through the second barrier layer by applying a voltage between the first electrode and the second electrode, and

wherein the first barrier layer is blocking the hole passed through the first barrier layer.

36. A light emitting device according to claim 34, wherein each of the light emitting layers includes an organic material.

37. An electronic device having the light emitting device according to claim 34, wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggles-type display, a car navigation system, a personal computer, a DVD player, an electronic game machine, or a portable information terminal.