Color filters for organic light-emissive devices

• US 6,861,799 B1
• Filed: 06/19/1998
• Issued: 03/01/2005
• Est. Priority Date: 06/21/1997
• Status: Expired due to Term

• Current Assignee: IPIFS Guarantee Corp.
• Original Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Inventors: Friend, Richard Henry, Pichler, Karl
• Primary Examiner(s): Patel, Vip
• Assistant Examiner(s): Zimmerman, Glenn
• Application Number:
  US09/446,476
• Time in Patent Office: 2,447 Days
• Field of Search: 313/504, 313/506, 313/112, 313/507, 313/501
• US Class Current: 313/504
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• CPC Class Codes: H05B 33/26 characterised by the composition or arrangement of the conductive material used as an electrode
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/17 Carrier injection layers
• CPC Class Codes: H10K 50/171 Electron injection layers
• CPC Class Codes: H10K 50/826 Multilayers, e.g. opaque multilayers
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/8791 Arrangements for improving contrast, e.g. preventing reflection of ambient light

Abstract

An electroluminescent device comprising: an organic light-emissive layer; an electrode on one side of the light-emissive layer for injecting charge carriers of a first polarity towards the light-emissive layer; and a light filtering layer on the other side of the light-emissive layer, the light filtering layer comprising an organic material that is doped to render it at least partially electrically conductive for injection of charge carriers of a second type towards the light-emissive layer.

Claims

1. An electroluminescent device comprising:

an organic light-emissive layer;

a first electrode on one side of the light-emissive layer for injecting charge carriers of a first polarity towards the light-emissive layer;

a light filtering layer on the other side of the light-emissive layer, the light filtering layer comprising an organic material that is doped to render it at least partially electrically conductive for injection of charge carriers of a second polarity towards the light-emissive layer, and wherein the light filtering layer is tailored to;

absorb an emission color of the light-emissive layer and emit light of a different color;

or

transmit an emission color of the light-emissive layer and absorb light of other colors; and

a second electrode on the other side of the light filtering layer from the light-emissive layer, for injecting charge carriers of a second polarity.

2. An electroluminescent device as claimed in claim 1, wherein the light filtering layer is a fluorescent filter.

3. An electroluminescent device as claimed in claim 2, wherein the light filtering layer is excitable to luminescence in the optical frequency range by light at at least some of the wavelengths at which the light-emissive layer is emissive.

4. An electroluminescent device as claimed in claim 1, further comprising a charge transport layer located between the light-emissive layer and the light filtering layer.

5. An electroluminescent device as claimed in claim 1, wherein the light filtering layer is adjacent to the light-emissive layer.

6. An electroluminescent device as claimed in claim 1, further comprising:

a charge transport layer between the first electrode and the light-emissive layer; and

at least one further region of light-emissive material laterally spaced from the light-emissive layer.

7. An electroluminescent device as claimed in claim 6, wherein the said further region is emissive with a different color from the light-emissive layer.

8. An electroluminescent device as claimed in claim 1, wherein the light-emissive layer comprises a conjugated polymer light-emissive material.

9. An electroluminescent device as claimed in claim 1, wherein the light filtering layer comprises a polymer material with the dopant.

10. An electroluminescent device as claimed in claim 1, wherein the light filtering layer is located outward of the light-emissive layer in the viewing direction, the light filtering layer having filtering characteristics such that it is capable of absorbing ambient light of at least some wavelengths which would otherwise impair the performance of the light-emissive layer.

11. An electroluminescent device as claimed in claim 10, wherein the light filtering layer is electrically conductive.

12. An electroluminescent device as claimed in claim 10, wherein the light filtering layer has low luminescence.

13. An electroluminescent device as claimed in claim 10, wherein the light filtering layer comprises at least two materials, at least one of which is a second organic light-emissive material and/or a light-absorptive material.

14. An electroluminescent device as claimed in claim 13, wherein the second light-emissive material is emissive with a different color of light from the light-emissive layer.

15. An electroluminescent device as claimed in claim 10, wherein the light-emissive layer comprises at least two independent light-emissive regions.

16. An electroluminescent device as claimed in claim 15, wherein the independent light-emissive regions are emissive with different colors of light from each other.

17. An electroluminescent device as claimed in claim 16, wherein the composition of the light filtering layer over each light-emissive region is tailored to the emission color of the respective light-emissive region.

18. An electroluminescent device as claimed in claim 10, wherein the light filtering layer comprises an organic material that is employed for light emission in the light-emissive layer.

19. An electroluminescent device as claimed in claim 10, wherein the light filtering layer is an ink-jet printed light-filtering layer.

20. An electroluminescent device as claimed in claim 1, further comprising a charge transport layer located between the light-emissive layer and the second electrode.

21. An electroluminescent device as claimed in claim 1, wherein the light filtering layer selectively shifts the emission that leaves the device.

22. An electroluminescent device as claimed in claim 1, wherein the light filtering layer selectively converts the light emitted from the light-emissive layer.

23. An electroluminescent device as claimed in claim 1, wherein the light filtering layer functions as a color band-pass or cut-off filter.

24. An electroluminescent device as claimed in claim 10, wherein the ambient light filtering layer restricts the passage of ambient light into the device.

25. An electroluminescent device as claimed in claim 10, wherein the ambient light filtering layer increases contrast by reducing photoluminescence due to one or more layers of the device being excited by ambient light.

26. An electroluminescent device as claimed in claim 10, wherein the ambient light filtering layer reduces photo-degradation of the device due to ambient light.

27. An electroluminescent device as claimed in claim 10, wherein the ambient light filtering layer reduces photo-conduction effects of the device due to ambient light.

28. An electroluminescent device comprising:

an organic light-emissive layer;

a first electrode on one side of the light-emissive layer for injecting charge carriers of a first polarity towards the light-emissive layer;

a light filtering layer on the other side of the light-emissive layer, the light filtering layer comprising an organic material that is doped to render it at least partially electrically conductive for injection of charge carriers of a second polarity towards the light-emissive layer;

a second electrode on the other side of the light filtering layer from the light-emissive layer, for injecting charge carriers of a second polarity,

wherein the light filtering layer is located outward of the light-emissive layer in the viewing direction, the light filtering layer having filtering characteristics such that it is capable of absorbing ambient light of at least some wavelengths which would otherwise impair the performance of the light-emissive layer;

wherein the light filtering layer has low luminescence, and

wherein emission from the device is not significantly affected by the light filtering layer.