Self-assembled transport layers for OLEDs

• US 6,850,003 B1
• Filed: 09/04/1998
• Issued: 02/01/2005
• Est. Priority Date: 09/05/1997
• Status: Expired due to Term

• Current Assignee: IPIFS Guarantee Corp.
• Original Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Inventors: Ho, Peter, Pichler, Karl, Bright, Chris, Greenham, Neil Clement, Friend, Richard Henry, Burroughes, Jeremy
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): HODGES, MATTHEW P
• Application Number:
  US09/508,034
• Time in Patent Office: 2,342 Days
• Field of Search: 427/469, 427/66, 427/430.1, 427/443.2, 427/458, 313/506
• US Class Current: 313/506
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 85/1135 Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
• CPC Class Codes: H10K 85/114 Poly-phenylenevinylene; Derivatives thereof
• CPC Class Codes: H10K 85/115 Polyfluorene; Derivatives thereof
• CPC Class Codes: H10K 85/141 comprising aliphatic or olefinic chains, e.g. poly N-vinylcarbazol, PVC or PTFE
• CPC Class Codes: H10K 85/151 Copolymers
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine

Abstract

Provided is a method of fabricating an organic light-emitting device; which method comprises the steps of: forming a first electrode (4) for the device over a substrate (2); either forming by self-assembly at least one polymer layer (6, 8) over the first electrode (4) and forming other than by self-assembly at least one layer of organic light emissive material (10) over the at least one polymer layer (6, 8); and forming a second electrode (12) for the device over the at least one layer of organic light emissive material (10); or forming other than by self-assembly at least one layer of organic light emissive material over the first electrode and forming by self-assembly at least one polymer layer over the at least one layer of organic light emissive material; and forming a second electrode for the device over the at least one polymer layer. Also provided is an organic light emitting device, obtainable according to the method of the present invention.

Claims

1. A method of fabricating an organic light-emitting device, which method comprises the steps of:

providing a substrate comprising a first electrode and a glass or a plastics material;

either forming by self-assembly at least one polymer layer over the first electrode and forming other than by self-assembly at least one layer of organic light emissive material over the at least one polymer layer; and

forming a second electrode for the device over the at least one layer of organic light emissive material;

or forming other than by self-assembly at least one layer of organic light emissive material over the first electrode and forming by self-assembly at least one polymer layer over the at least one layer of organic light emissive material; and

forming a second electrode for the device over the at least one polymer layer; and

removing physisorbed water from the surface of the substrate prior to forming the at least one polymer layer, wherein the physisorbed water is removed by heating.

2. A method according to claim 1, which method further comprises forming a coupling layer prior to forming the at lest one polymer layer.

3. A method according to claim 2, wherein the coupling layer is formed by silylating the substrate.

4. A method according to claim 1, which method further comprises preparing the substrate surface such that the surface charge of the substrate is pH independent.

5. A method according to claim 1, wherein the substrate comprises amino groups, the method further comprises quaternising amino groups to form positively charged quaternised species on the surface.

6. A method according to claim 1, wherein when the substrate comprises thiol groups, the method further comprises the step of oxidizing thiol groups to form negatively charged species on the surface.

7. A method according to claim 1, wherein the plastics material comprises one or more of a polyester, a polycarbonate or a poly(ether amide).

8. A method according to claim 1, wherein the at least one self-assembled polymer layer comprises one or more pairs of co-operating sub-layers.

9. A method according to claim 8, wherein the one or more pairs of co-operating sub-layers interact by attractive forces, each sub-layer being dissimilar to the other.

10. A method according to claim 9, wherein one sub-layer of a pair is negatively charged and the other sub-layer of the pair is positively charged.

11. A method according to claim 8, wherein the one or more pairs of co-operating sublayers interact by donor/acceptor interaction.

12. A method according to claim 11, wherein the donor/acceptor interaction is provided by hydrogen bonding.

13. A method according to claim 8, wherein each sub-layer of the cooperating pairs of sub-layers is 0.3-2 nm thick.

14. A method according to claim 1, wherein the at least one polymer layer is 0.3-20 nm thick.

15. A method according to claim 1, wherein the organic material comprises a conjugated polymer and/or a low molecular weight compound.

16. A method according to claim 15, wherein the organic material comprises a semi conductive conjugated polymer.

17. A method according to claim 16, wherein the organic material comprises PPV or a derivative thereof.

18. A method according to claim 1, wherein the at least one layer of organic light-emissive material is 30-1000 nm thick.

41. An organic light emitting device, obtainable according to a method as defined in claim 1.

19. A method of fabricating an organic light-emitting device which method comprises the steps of:

forming a first electrode for the device over a substrate, wherein said substrate comprises a glass or a plastics material;

either removing physisorbed water by heating from the surface of the first electrode, forming a coupling layer, forming, by self-assembly, at least one polymer layer over the first electrode, and forming at least one layer of organic light emissive material over the at least one polymer layer;

or forming at least one layer of organic light emissive material over the first electrode, removing physisorbed water by heating from the surface of the at least one organic light-emissive material, forming a coupling layer, and forming, by self-assembly, at least one polymer layer over the at least one layer of light emissive material; and

forming a second electrode for the device over the at least one layer of light emissive material.

20. A method according to claim 19, wherein the at least one polymer layer has an electronic and/or optical property that varies across the thickness of the layer.

21. A method according to claim 20, which method additionally comprises the step of processing the at least one polymer layer to form the spatial variation in the electronic and/or optical property.

22. A method according to claim 21, wherein the at least one polymer layer comprises a conjugated material and the step of forming the spatial variation in the electronic and/or optical property comprises reducing the degree of conjugation of the conjugated material.

23. A method according to claim 21, wherein the step of processing the at least one polymer layer comprises exposing the polymer layer to a reactive agent to promote a chemical reaction in the at least one polymer layer.

24. A method according to claim 23, wherein the reaction is an oxidation or reduction reaction.

25. A method according to claim 23, wherein the reactive agent is an oxidizing agent.

26. A method according to claim 23, wherein the agent is oxygen.

27. A method according to claim 23, wherein the agent is in the form of a plasma.

28. A method according to claim 20, wherein the step of forming the at least one polymer layer comprises forming the polymer layer in a state in which the electronic and/or optical property varies across its thickness.

29. A method according to claim 28, wherein the polymer layer is deposited in a series of sub-layers.

30. A method according to claim 28, wherein the polymer layer is deposited in the form of a series of bi-layers each containing two sub-layers of different materials.

31. A method according to claim 28, wherein the polymer layer is deposited so as to comprise a series of sub-layers of a material which each differ in the electronic and/or optical property.

32. A method according to claim 31, wherein the sub-layers of a material are graded in the said property across the thickness of the polymer layer.

33. A method according to claim 31, wherein the material comprises poly(styrenesulphonic acid).

34. A method according to claim 31, wherein the sub-layers are doped so as to achieve the difference in the electronic and/or optical property.

35. A method according to claim 33, wherein in at least some of the sub-layers the poly(styrenesulphonic acid) is doped with poly(ethylenedioxythiophene).

36. A method according to claim 20, wherein said property is an energy level or an energy level distribution.

37. A method according to claim 36, wherein said property is ionisation potential.

38. A method according to claim 20, wherein in a direction from the first electrode to the light emissive layer the ionisation potential of the polymer layer varies away from the conduction band of the first electrode.

39. A method according to claim 20, wherein in a direction from the first electrode to the light emissive layer the ionisation potential of the polymer layer varies towards the HOMO level of the light emissive layer.

40. A method according to claim 20, wherein the optical gap of the light emissive layer varies in a direction from the first electrode to the second electrode.

42. An organic light emitting device comprising:

at least one layer of organic light-emissive material between a first electrode and a second electrode, the at least one organic light-emissive material having been formed other than by self-assembly; and

at least one polymer layer between one of the first and second electrodes and the at least one organic light-emissive material, the at least one polymer layer being formed by self-assembly, wherein the at least one polymer layer has an electronic and/or optical property that varies across the thickness of the layer.

43. A method of fabricating an organic light-emitting device, which method comprises the steps of:

providing a substrate comprising a first electrode and a glass or a plastics material;

either forming by self-assembly at least one polymer layer over the first electrode and forming other than by self-assembly at least one layer of organic light emissive material over the at least one polymer layer; and

forming a second electrode for the device over the at least one layer of organic light emissive material;

or forming other than by self-assembly at least one layer of organic light emissive material over the first electrode and forming by self-assembly at least one polymer layer over the at least one layer of organic light emissive material; and

forming a second electrode for the device over the at least one polymer layer;

wherein the at least one self-assembled polymer layer comprises one or more pairs of co-operating sub-layers, and wherein the one or more pairs of co-operating sub-layers interact by donor/acceptor interaction.

44. A method of fabricating an organic light-emitting device which method comprises the steps of:

forming a first electrode for the device over a substrate, wherein said substrate comprises a glass or a plastics material;

either removing physisorbed water from the surface of the first electrode, forming a coupling layer, forming, by self-assembly, at least one polymer layer over the first electrode, and forming at least one layer of organic light emissive material over the at least one polymer layer;

or forming at least one layer of organic light emissive material over the first electrode, removing physisorbed water from the surface of the at least one organic light-emissive material, forming a coupling layer, and forming, by self-assembly, at least one polymer layer over the at least one layer of light emissive material; and

forming a second electrode for the device over the at least one layer of light emissive material, wherein the at least one polymer layer has an electronic and/or optical property that varies across the thickness of the layer.