Organic electroluminescent element having electrode between two fluorescent media for injecting carrier thereinto

• US 5,837,391 A
• Filed: 01/16/1997
• Issued: 11/17/1998
• Est. Priority Date: 01/17/1996
• Status: Expired due to Term

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Utsugi, Koji
• Primary Examiner(s): COONEY, JOHN M
• Application Number:
  US08/784,791
• Time in Patent Office: 670 Days
• Field of Search: 428/690, 428/917, 313/504, 313/505, 313/506, 313/503
• US Class Current: 428/690
• CPC Class Codes: H05B 33/12 Light sources with substantially two-dimensional radiating surfaces
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

An organic electroluminescent element has a semi-transparent anode or a semi-transparent cathode inserted between luminescent media for injecting holes thereinto, and the semi-transparent anode or the semi-transparent cathode improves the carrier injecting efficiency so as to enhance the luminance.

Claims

1. An organic electroluminescent element comprising:

a multi-layer structure having a plurality of thin films which form a plurality of boundaries therebetween, said plurality of thin films including

a first organic luminescent layer for emitting light in a first color,

a second organic luminescent layer for emitting light in a second color different from said first color,

a third organic luminescent layer for emitting light in a third color different from said first and second colors; and

a plurality of electrodes selectively connected to a first source of power voltage and a second source of power voltage different in potential level from said first source of power voltage for applying potentials to said first, second and third organic luminescent layers, and including at least one electrode provided at one of said plurality of boundaries for injecting first electric charges into two of said first, second and third organic luminescent layers and other electrodes injecting second electric charges opposite in polarity to said first electric charges into said two of said first, second and third organic luminescent layers.

2. The organic electroluminescent element as set forth in claim 1, in which said multi-layer structure is sandwiched between said other electrodes.

3. The organic electroluminescent element as set forth in claim 2, in which said at least one electrode is inserted between said second organic luminescent layer for green light and said third organic luminescent layer for red light for injecting holes into said second and third organic luminescent layers, and said other electrodes inject electrons into said first and second organic luminescent layers and said third organic luminescent layer so as to emit a blue light, a green light and a red light from said first, second and third organic luminescent layers through a recombination between said holes and said electrons.

4. The organic electroluminescent element as set forth in claim 3, in which said plurality of thin films further include hole transporting layers inserted between said at least one electrode and said second and third organic luminescent layers.

5. The organic electroluminescent element as set forth in claim 4, in which said plurality of thin films further include blocking layers inserted between said hole transporting layers and said second and third organic luminescent layers so as to confine excitons generated in said first, second and third organic luminescent layers.

6. The organic electroluminescent element as set forth in claim 4, in which said plurality of thin films further include hole injecting layers between said at least one electrode and said hole transporting layers for stably injecting said holes into said second and third organic luminescent layers.

7. The organic electroluminescent element as set forth in claim 3, in which said plurality of thin films further include electron injecting and electron transporting layers between said other electrodes and said first and third organic luminescent layers, respectively.

8. The organic electroluminescent element as set forth in claim 2, in which said at least one electrode is inserted between said first organic luminescent layer for blue light and said second organic luminescent layer for green light for injecting holes into said first and second organic luminescent layers, and said other electrodes inject electrons into said first organic luminescent layer and said second and third organic luminescent layers so as to emit a blue light, a green light and a red light from said first, second and third organic luminescent layers through a recombination between said holes and said electrons.

9. The organic electroluminescent element as set forth in claim 8, in which said plurality of thin films further include hole transporting layers inserted between said at least one electrode and said first and second organic luminescent layers.

10. The organic electroluminescent element as set forth in claim 9, in which said plurality of thin films further include blocking layers inserted between said hole transporting layers and said first and second organic luminescent layers so as to confine excitons generated in said first, second and third organic luminescent layers.

11. The organic electroluminescent element as set forth in claim 9, in which said plurality of thin films further include hole injecting layers between said at least one electrode and said hole transporting layers for stably injecting said holes into said first and second organic luminescent layers.

12. The organic electroluminescent element as set forth in claim 1, in which one of said other electrodes is provided at another of said plurality of boundaries, and said multilayer structure is sandwiched between another of said other electrodes and yet another electrode.

13. The organic electroluminescent element as set forth in claim 12, in which said at least one electrode and said yet another electrode inject electrons into said first, second and third organic luminescent layers, and said one of said other electrodes and said another of said other electrodes inject holes into said first, second and third organic luminescent layers so as to emit a blue light, a green light and a red light from said first, second and third organic luminescent layers through a recombination of said holes and said electrons.

14. The organic electroluminescent element as set forth in claim 13, in which said at least one electrode and said one of said other electrodes are inserted between said first organic luminescent layer and said second organic luminescent layer and between said second organic luminescent layer, respectively and said third organic luminescent layer.

15. The organic electroluminescent element as set forth in claim 14, in which said plurality of thin films further include hole transporting layers between said another of said other electrodes and said first organic luminescent layer and between said one of said other electrodes and said second and third organic luminescent layers.

16. The organic electroluminescent element as set forth in claim 15, in which said plurality of thin films further include blocking layers between the hole transporting layers and said first, second and third organic luminescent layers.

17. The organic electroluminescent element as set forth in claim 15, in which said plurality of thin films further include hole injecting layers between said another of said other electrodes and the hole transporting layer held in contact with said first organic luminescent layer and between said one of said other electrodes and the hole transporting layers respectively held in contact with said second and third organic luminescent layers.

18. The organic electroluminescent layer as set forth in claim 14, in which said plurality of thin films further include electron injecting and electron transporting layers between said at least one electrode and said first and second organic luminescent layers and between said yet another electrode and said third organic luminescent layer.