Light-emitting element having hole generating layer

• US 7,462,883 B2
• Filed: 08/03/2005
• Issued: 12/09/2008
• Est. Priority Date: 08/04/2004
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Satoshi, Kumaki, Daisuke
• Primary Examiner(s): Dickey; Thomas L
• Application Number:
  US11/195,623
• Publication Number:
  US 20060027830A1
• Time in Patent Office: 1,224 Days
• Field of Search: 257/103, 257/E51.051, 313/504, 313/506
• US Class Current: 257/103
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/15 Hole transporting layers
• CPC Class Codes: H10K 50/155 comprising dopants
• CPC Class Codes: H10K 50/157 between the light-emitting layer and the cathode
• CPC Class Codes: H10K 50/16 Electron transporting layers
• CPC Class Codes: H10K 50/165 comprising dopants
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays

Abstract

The present invention provides a light-emitting element having a structure in which the drive voltage is comparatively low and a light-emitting element in which the increase in the drive voltage over time is small. Further, the present invention provides a display device in which the drive voltage and the increase in the drive voltage over time are small and which can resist long-term use. A layer in contact with an electrode in a light-emitting element is a layer containing a P-type semiconductor or a hole-generating layer such as an organic compound layer containing a material having electron-accepting properties. The light-emitting layer is sandwiched between the hole-generating layers, and an electron-generating layer is sandwiched between the light-emitting layer and the hole-generating layer on a cathode side.

Claims

1. A light-emitting element comprising:

an anode and a cathode;

a first layer between the anode and the cathode, said first layer generating holes;

a second layer between the anode and the cathode, said second layer generating holes and contacting the cathode;

a third layer between the first layer and the second layer, wherein said third layer is a light emitting layer including a light emitting material; and

a fourth layer between the second layer and the third layer, said fourth layer generating electrons,

wherein the second layer comprises a metal oxide.

2. A light-emitting element comprising:

an anode and a cathode;

a first layer between the anode and the cathode, said first layer including a first P-type semiconductor material;

a second layer between the anode and the cathode, said second layer including a second P-type semiconductor material and contacting the cathode;

a third layer between the first layer and the second layer, wherein said third layer is a light emitting layer including a light emitting material; and

a fourth layer between the second layer and the third layer, said fourth layer including an N-type semiconductor material,

wherein the second P-type semiconductor material is a metal oxide.

3. The light-emitting element according to claim 2,

wherein the first P-type semiconductor material is a metal oxide.

4. The light-emitting element according to claim 2,

wherein each of the first P-type semiconductor material and the second P-type semiconductor material is at least one compound selected from the group consisting of vanadium oxide, molybdenum oxide, cobalt oxide, and nickel oxide.

5. The light-emitting element according to claim 2,

wherein the N-type semiconductor material is metal oxide.

6. The light-emitting element according to claim 2,

wherein the N-type semiconductor material is at least one compound selected from the group consisting of zinc oxide, zinc sulfide, zinc selenide, and titanium oxide.

7. A light-emitting element comprising:

an anode and a cathode;

a first layer between the anode and the cathode, said first layer including a P-type semiconductor material;

a second layer between the anode and the cathode, said second layer including the P-type semiconductor material and contacting the cathode;

a third layer between the first layer and the second layer, said third layer including a light emitting material; and

a fourth layer between the second layer and the third layer, said fourth layer including an N-type semiconductor material,

wherein the P-type semiconductor material is a metal oxide.

8. The light-emitting element according to claim 7,

wherein the P-type semiconductor material is at least one compound selected from the group consisting of vanadium oxide, molybdenum oxide, cobalt oxide, and nickel oxide.

9. The light-emitting element according to claim 7,

wherein the N-type semiconductor material is metal oxide.

10. The light-emitting element according to claim 7,

wherein the N-type semiconductor material is at least one compound selected from the group consisting of zinc oxide, zinc sulfide, zinc selenide, and titanium oxide.

11. A light-emitting element comprising:

an anode and a cathode;

a first layer between the anode and the cathode, said first layer including a first organic compound and a first material having electron-accepting properties to the first organic compound;

a second layer between the anode and the cathode, said second layer including a second organic compound and a second material having electron-accepting properties to the second organic compound;

a third layer between the first layer and the second layer, said third layer including a light emitting material; and

a fourth layer between the second layer and the third layer, said fourth layer including a third organic compound and a third material having electron-donating properties to the third organic compound,

wherein the second layer is in contact with the cathode.

12. The light-emitting element according to claim 11,

wherein the third organic compound is an organic compound having electron-transporting properties.

13. The light-emitting element according to claim 11,

wherein the third material includes one of alkali metal, alkali-earth metal, and rare-earth metal.

14. The light-emitting element according to claim 11,

wherein each of the first organic compound and the second organic compound is an organic compound having hole-transporting properties.

15. The light-emitting element according to claim 11,

wherein each of the first material and the second material is metal oxide.

16. A light-emitting element comprising:

an anode and a cathode;

a first layer between the anode and the cathode, said first layer including a first organic compound and a first material having electron-accepting properties to the first organic compound;

a second layer between the anode and the cathode, said second layer including the first organic compound and the first material having electron-accepting properties to the first organic compound;

a third layer between the first layer and the second layer, said third layer including a light emitting material; and

a fourth layer between the second layer and the third layer, said fourth layer including a second organic compound and a second material having electron-donating properties to the second organic compound,

wherein the second layer is in contact with the cathode.

17. The light-emitting element according to claim 16,

wherein the second organic compound is an organic compound having electron-transporting properties.

18. The light-emitting element according to claim 16,

wherein the second material includes one of alkali metal, alkali-earth metal, and rare-earth metal.

19. The light-emitting element according to claim 16,

wherein the first organic compound is an organic compound having hole-transporting properties.

20. The light-emitting element according to claim 16,

wherein the first material is metal oxide.