Distributed bragg reflector, organic light emitting element, and multicolour light emitting device

• US 6,756,732 B1
• Filed: 08/31/2001
• Issued: 06/29/2004
• Est. Priority Date: 11/26/1999
• Status: Expired due to Term

• Current Assignee: Cambridge University (Government of United Kingdom)
• Original Assignee: Cambridge University (Government of United Kingdom)
• Inventors: Kawase, Takeo
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): Guharay, Karabi
• Application Number:
  US09/890,060
• Time in Patent Office: 1,033 Days
• Field of Search: 313/504, 313/506, 313/511, 313/498, 313/110, 313/113, 272/92, 359/586, 359/587, 359/589, 428/917, 428/212, 428/690, 438/29
• US Class Current: 313/504
• CPC Class Codes: G02B 5/0841 comprising organic materials, e.g. polymers
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair

Abstract

A distributed Bragg reflector comprising a stack of alternate layers of a first material and a second material wherein the first and second materials are both organic materials. An organic electroluminescent light emitting element comprising: a transparent substrate, a transparent electrode formed on the substrate, a distributed Bragg reflector formed on the transparent electrode, an organic electroluminescent light emitting material formed on the distributed Bragg reflector, and an electrode formed on the light emitting material.

Claims

1. A distributed Bragg reflector comprising a stack of alternate layers of a first material and a second material, wherein the first and second materials are both organic materials and the difference in HOMO energy levels of the first and second materials is less than 0.6 eV.

2. A distributed Bragg reflector as claimed in claim 1, wherein the first and second materials are both polymer materials.

3. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises a conjugated polymer to which non-conjugated side groups have been added.

4. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises a co-polymer having two groups, one of which is a non-conjugated polymer group.

5. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises a blend or mixture of polymers.

6. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials is soluble in an organic solvent other than methanol but not soluble in water or methanol and the other of the said materials is soluble in water or methanol and not soluble in the said organic solvent.

7. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises poly-3,4-ethylenedioxythiophene.

8. A distributed Bragg reflector as claimed in claim 7, wherein the poly-3,4-ethylenedioxythiophene is doped with PSS.

9. A distributed Bragg reflector as claimed in claim 8, wherein the PSS doped poly-3,4-ethylenedioxythiophene is diluted with polyvinylalcohol, or polyacrylate, or polymethacrylate.

10. A distributed Bragg reflector as claimed in claim 7, wherein the poly-3,4-ethylenedioxythiophene is doped with a dye.

11. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises a polyfluorene derivative.

12. A distributed Bragg reflector as claimed in claim 11, wherein the polyfluorene derivative is poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine).

13. A distributed Bragg reflector as claimed in claim 12, wherein the poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) is blended with poly(9,9-dioctylfluorene-co-2,1,3-benzothiadizole).

14. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises poly(9,9-dioctylfluorene) and the other of said materials comprises poly(9,9-dioctylfluorene-co-2,1,3-benzothiadizole).

15. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises poly(9,9-dioctylfluorene) and the other of said materials comprises poly(9,9-dihexylfluorene).

16. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises poly-3,4-ethylenedioxythiophene and the other of said materials comprises aluminum chelate.

17. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) and the other of said materials comprises aluminum chelate.

18. A distributed Bragg reflector as claimed in claim 1, wherein one of the first and second materials comprises poly(9,9-dioctylfluorene-co-bis-N,N′

-(4-methoxyphenyl)-bis-N, N′

phenyl-1,4-phenylenediamine).

19. An organic electroluminescent light emitting element comprising:

a transparent substrate;

a transparent electrode formed on the substrate;

a distributed Bragg reflector formed on the transparent electrode;

an organic electroluminescent light emitting material formed on the distributed Bragg reflector; and

an electrode formed on the light emitting material, the distributed Bragg reflector comprising a stack of alternate layers of a first material and a second material, wherein the first and second material are both organic materials.

20. An organic electroluminescent light emitting element as claimed in claim 19, wherein one of the first and second materials has a peak absorption wavelength which is longer than the mode wavelength of the device.

21. An organic electroluminescent light emitting element as claimed in claim 19, wherein the light emitting material is poly(9,9-dioctylfluorene-co-2,1,3-benzothiadizole).

22. A multicolour light emitting device comprising a plurality of light emitting elements as claimed in claim 19.

23. A multicolour light emitting device as claimed in claim 22, wherein the first and second materials are formed in different thickness layers and provide different mode wavelength areas on the substrate.

24. A method of manufacturing an organic electro-luminescent light emitting element, comprising the steps of:

providing a transparent substrate;

forming a transparent electrode formed on the substrate;

forming a distributed Bragg reflector on the transparent electrode by forming a stack of alternate layers of a first organic material and a second organic material using inkjet technology;

forming an organic electroluminescent light emitting material on the distributed Bragg reflector; and

forming an electrode on the light emitting material.

25. A method of manufacturing a multicolour light emitting device comprising the steps of:

forming a plurality of light emitting elements using the method of claim 24; and

forming therein the first and second materials in different thickness layers to provide different mode wavelength areas on the substrate.