Color variable bipolar/AC light-emitting devices

• US 6,235,414 B1
• Filed: 03/11/1998
• Issued: 05/22/2001
• Est. Priority Date: 03/11/1997
• Status: Expired due to Term

• Current Assignee: The Ohio State University Research Foundation
• Original Assignee: The Ohio State University Research Foundation
• Inventors: Epstein, Arthur J., Wang, Yunzhang
• Primary Examiner(s): YAMNITZKY, MARIE ROSE
• Application Number:
  US09/038,226
• Time in Patent Office: 1,168 Days
• Field of Search: 313/504, 313/506, 428/212, 428/690, 428/917, 257/40, 257/89, 257/90, 257/94, 257/96, 257/103
• US Class Current: 428/690
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 85/10 Organic polymers or oligomers
• CPC Class Codes: H10K 85/111 comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
• CPC Class Codes: H10K 85/113 Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/114 Poly-phenylenevinylene; Derivatives thereof
• CPC Class Codes: H10K 85/151 Copolymers
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

Color-variable light-emitting devices which are capable of generating two independent colors, even at room temperature. The devices comprise a layer of at least one active electroluminescent polymer. This electroluminescent polymer may be accompanied by one or two redox-mediating polymer layers. The redox polymer layer(s) modify the charge injection and transport properties such that the device may be operated under both forward and reverse bias.

Claims

1. A color-variable electroluminescent device comprising:

(a) a polymeric layer adapted to act as a light emitting layer, said polymeric layer comprising a blend of at least two emissive polymers having different emissive and charge transport properties such that said blended polymeric layer is capable of conducting current in opposing directions; and

(b) two electrodes disposed respectively on either side of said polymeric layer, said polymeric layer being in electrical contact with said electrodes so as to be capable of producing a color variable light emission upon a current being passed in different directions through said polymeric layer, said color of said light emission dependent upon said direction of said current.

2. An electroluminescent device according to claim 1 wherein said polymeric layer comprises a blend of polymers selected from the group consisting of conjugated polymers and copolymers.

3. An electroluminescent device according to claim 1 wherein said polymeric layer comprises a polymer selected from the group consisting of polypyridines, polypyridylvinylenes, polythiophenes, polyphenylenes, polyphenylenevinylenes, polyphenylenebenzobisthiazoles, polyfluorenes, polyvinylcarbazoles, polyacetylenes and polythienylenevinylenes.

4. An electroluminescent device according to claim 1 wherein said polymeric layer comprises a blend of poly(pyridyl vinylene/phenylene vinylene) and poly(phenylene/thiophene).

5. An electroluminescent device according to claim 1 wherein a said electrode comprises a material selected from the group consisting of aluminum and indium-tin-oxides.

6. An electroluminescent device according to claim 1 additionally comprising a source of a direct electric current supplied to said electrodes.

7. An electroluminescent device according to claim 1 additionally comprising a source of an alternating electric current supplied to said electrodes.

8. A color-variable electroluminescent device comprising:

(a) a first non-emissive polymeric layer;

(b) a second non-emissive polymeric layer;

(c) an intermediate polymeric layer adapted to act as a light emitting layer and disposed between said first non-emissive polymeric layer and said second non-emissive polymeric layer and capable of conducting current in opposing directions, at least one of said non-emissive polymer layers adapted to modify the emission properties of said intermediate polymeric layer such that an interface between said light emitting layer and said at least one non-emissive polymer layer is adapted to emit light of a different color than said light emitting layer; and

(d) two electrodes in electrical contact respectively with said first non-emissive polymeric layer and said second non-emissive polymeric layer, said intermediate polymeric layer being in electrical contact with said first non-emissive polymeric layer and said second non-emissive polymeric layer so as to be capable of producing a color-variable light emission upon a current being passed in different directions through said intermediate polymeric layer, said color of said light emission dependent upon said direction of said current.

9. An electroluminescent device according to claim 8 wherein said intermediate polymeric layer comprises a blend of polymers selected from the group consisting of conjugated polymers and copolymers.

10. An electroluminescent device according to claim 8 wherein said intermediate polymeric layer comprises a blend of poly(pyridyl vinylene/phenylene vinylene) and poly(phenylene/thiophene).

11. An electroluminescent device according to claim 8 wherein said polymeric layer comprises a polymer selected from the group consisting of polypyridines, polypyridylvinylenes, polythiophenes, polyphenylenes, polyphenylenevinylenes, polyphenylenebenzobisthiazoles, polyfluorenes, polyvinylcarbazoles, polyacetylenes and polythienylenevinylenes.

12. An electroluminescent device according to claim 8 wherein a said electrode comprises a material selected from the group consisting of aluminum and indium-tin-oxides.

13. An electroluminescent device according to claim 8 additionally comprising a source of a direct electric current supplied to said electrodes.

14. An electroluminescent device according to claim 8 additionally comprising a source of an alternating electric current supplied to said electrodes.

15. An electroluminescent device according to claim 8 wherein said first non-emissive polymeric layer comprises a material selected from the group consisting of emeraldine base polyaniline, oligomers of emeraldine base polyaniline, sulfonated polyaniline, oligomers of sulfonated polyaniline, and mixtures thereof.

16. An electroluminescent device according to claim 8 wherein said second non-emissive polymeric layer comprises a material selected from the group consisting of emeraldine base polyaniline, oligomers of emeraldine base polyaniline, sulfonated polyaniline, oligomers of sulfonated polyaniline, and mixtures and ring-substituted derivatives thereof.

17. An electroluminescent device according to claim 8 wherein said intermediate polymeric layer comprises polymers selected from the group consisting of both copolymers and oligomers of both conjugated polymers and non-conjugated polymers.

18. An electroluminescent device according to claim 8 wherein said intermediate polymeric layer comprises at least one molecular dopant.

19. A color-variable electroluminescent device comprising:

(a) a non-emissive polymeric layer;

(b) two electrodes, a first electrode in electrical contact with said non-emissive polymeric layer, and a second electrode; and

(c) an intermediate polymeric layer comprising a blend of at least two emissive polymers having different emissive and charge transport properties, said intermediate polymer layer adapted to act as a light emitting layer and disposed between said non-emissive polymeric layer and said second electrode and capable of conducting current in opposing directions, said intermediate polymeric layer being in electrical contact with said non-emissive polymeric layer so as to be capable of producing a color-variable light emission upon a current being passed in different directions through said intermediate polymeric layer, said color of said light emission dependent upon said direction of said current.

20. An electroluminescent device according to claim 19 wherein said intermediate polymeric layer comprises a blend of polymers selected from the group consisting of conjugated polymers and copolymers.

21. An electroluminescent device according to claim 19 wherein said intermediate polymeric layer comprises a blend of poly(pyridyl vinylene/phenylene vinylene) and poly(phenylene/thiophene).

22. An electroluminescent device according to claim 19 wherein said polymeric layer comprises a polymer selected from the group consisting of polypyridines, polypyridylvinylenes, polythiophenes, polyphenylenes, polyphenylenevinylenes, polyphenylenebenzobisthiazoles, polyfluorenes, polyvinylcarbazoles, polyacetylenes and polythienylenevinylenes.

23. An electroluminescent device according to claim 19 wherein a said electrode comprises a material selected from the group consisting of aluminum and indium-tin-oxides.

24. An electroluminescent device according to claim 19 additionally comprising a source of a direct electric current supplied to said electrodes.

25. An electroluminescent device according to claim 19 additionally comprising a source of an alternating electric current supplied to said electrodes.

26. An electroluminescent device according to claim 19 wherein said non-emissive polymeric layer comprises a material selected from the group consisting of emeraldine base polyaniline, oligomers of emeraldine base polyaniline, sulfonated polyaniline, oligomers of sulfonated polyaniline, and mixtures and ring-substituted derivatives thereof.

27. An electroluminescent device according to claim 19 wherein said intermediate polymeric layer comprises polymers selected from the group consisting of both copolymers and oligomers of both conjugated polymers and non-conjugated polymers.

28. An electroluminescent device according to claim 19 wherein said intermediate polymeric layer comprises at least one molecular dopant.