Reduction or elimination of color change with viewing angle for microcavity devices

• US 20060066220A1
• Filed: 09/27/2004
• Published: 03/30/2006
• Est. Priority Date: 09/27/2004
• Status: Abandoned Application

• Current Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Original Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Inventors: So, Franky, Choong, Vi-En
• Application Number:
  US10/951,514
• Publication Number:
  US 20060066220A1
• Time in Patent Office: Days
• US Class Current: 313/501
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 59/876 comprising a resonant cavity structure, e.g. Bragg reflector pair

Abstract

In an embodiment of the invention, a microcavity OLED device that minimizes or eliminates color change at different viewing angles is fabricated. This OLED device includes a multi-layer mirror on a substrate, and each of the layers are comprised of a non-absorbing material. The OLED device also includes a first electrode on the multi-layered first mirror, and the first electrode is substantially transparent. An emissive layer is on the first electrode. A second electrode is on the emissive layer, and the second electrode is substantially reflective and functions as a mirror. The multi-layer mirror and the second electrode form a microcavity that amplifies a particular wavelength that is in resonance with an optical length of the microcavity. The emissive layer is comprised of a material that has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a wavelength at which a color change begins to occur.

Claims

1. A microcavity OLED device that minimizes or eliminates color change at different viewing angles, comprising:

a substrate;

a multi-layer mirror on said substrate, wherein said multi-layer mirror is comprised of a plurality of layers, each of said plurality of layers is comprised of a non-absorbing material;

a first electrode on said multi-layered first mirror, wherein said first electrode is substantially transparent;

an emissive layer on said first electrode; and

a second electrode on said emissive layer, wherein said second electrode is a mirror,

wherein said multi-layer mirror and said second electrode form a microcavity that amplifies a particular wavelength that is in resonance with an optical length of said microcavity, and

wherein said emissive layer is comprised of a material that has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a wavelength at which a color change begins to occur.

2. The OLED device of claim 1 wherein said material has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a resonant optical length of said microcavity at 0°

viewing angle minus 20 nm.

3. The OLED device of claim 2 wherein said emission spectrum is asymmetrical and has a sharp intensity drop-off on a shorter wavelength side from a peak emitted wavelength, and said peak emitted wavelength is at a desired color.

4. The OLED device of claim 2 wherein said emission spectrum is a narrow emission spectrum.

5. The OLED device of claim 1 wherein at a large viewing angle where said microcavity is amplifying a shorter wavelength with insignificant intensity, a peak emitted wavelength at said large viewing angle is close to a peak emitted wavelength from said microcavity at said 0°

viewing angle.

6. The OLED device of claim 1 wherein at a large viewing angle where said microcavity is amplifying a shorter wavelength with insignificant intensity, said resonant wavelength is different than a peak emitted wavelength from said microcavity at said large viewing angle.

7. The OLED device of claim 1 wherein said color change begins to occur when a wavelength emits a different hue than that of said peak emitted wavelength from said microcavity at a 0°

viewing angle.

8. The OLED device of claim 2 wherein said intensity of said luminance components at wavelengths shorter than said resonant optical length of said microcavity at 0°

viewing angle minus 20 nm is less than 5% of an intensity of a peak emitted wavelength of said material.

9. The OLED device of claim 1 wherein a peak emitted wavelength from said microcavity at any viewing angle is close to a peak emitted wavelength of said material.

10. The OLED device of claim 1 wherein adjacent layers of said multi-layer mirror have different refractive indexes.

11. The OLED device of claim 1 wherein a particular one of said adjacent layers has a high refractive index and another one of said adjacent layers has a low refractive index.

12. The OLED device of claim 1 wherein said first electrode is an anode, and further comprising a hole transport layer on said anode, wherein said hole transport layer is between said anode and said emissive layer.

13. The OLED device of claim 1 wherein said OLED device is an OLED display or an OLED light source used for area illumination.

14. A method to fabricate a microcavity OLED device that minimizes or eliminates color change at different viewing angles, comprising:

forming a multi-layer mirror on a substrate, wherein said multi-layer mirror is comprised of a plurality of layers, each of said plurality of layers is comprised of a non-absorbing material;

forming a first electrode on said multi-layer mirror, wherein said first electrode is substantially transparent;

forming an emissive layer on said first electrode; and

forming a second electrode on said emissive layer, wherein said second electrode is a mirror,

wherein said multi-layer mirror and said second electrode form a microcavity that amplifies a particular wavelength that is in resonance with an optical length of said microcavity, and

wherein said emissive layer is comprised of a material that has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a wavelength at which a color change begins to occur.

15. The method of claim 14 wherein said material has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a resonant optical length of said microcavity at 0°

viewing angle minus 20 nm.

16. The method of claim 15 wherein said emission spectrum is asymmetrical and has a sharp intensity drop-off on a shorter wavelength side from a peak emitted wavelength, and said peak emitted wavelength is at a desired color.

17. The method of claim 15 wherein said emission spectrum is a narrow emission spectrum.

18. The method of claim 14 wherein said color change begins to occur when a wavelength emits a different hue than that of said peak emitted wavelength.

19. The method of claim 15 wherein said intensity of said luminance components at wavelengths shorter than said resonant optical length of said microcavity at 0°

viewing angle minus 20 nm is less than 5% of an intensity of a peak emitted wavelength of said material.

20. The method of claim 14 wherein adjacent layers of said multi-layer mirror have different refractive indexes.

21. The method of claim 14 wherein said first electrode is an anode, and further comprising forming a hole transport layer on said anode, wherein said hole transport layer is between said anode and said emissive layer.

22. A top-emitting microcavity OLED device that minimizes or eliminates color change at different viewing angles, comprising:

a substrate;

a first electrode on said substrate, wherein said first electrode is a mirror;

an emissive layer on said first electrode; and

a second electrode on said emissive layer, wherein said second electrode is substantially transparent; and

a multi-layer mirror on said second electrode, wherein said multi-layer mirror is comprised of a plurality of layers, each of said plurality of layers is comprised of a non-absorbing material,

wherein said first electrode and said multi-layer mirror form a microcavity that amplifies a particular wavelength that is in resonance with an optical length of said microcavity, and

wherein said emissive layer is comprised of a material that has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a wavelength at which a color change begins to occur.

23. The OLED device of claim 22 wherein said material has an emission spectrum with no luminance components with significant intensity at wavelengths shorter than a resonant optical length of said microcavity at 0°

viewing angle minus 20 nm.

24. The OLED device of claim 22 wherein at a large viewing angle where said microcavity is amplifying a shorter wavelength with insignificant intensity, a peak emitted wavelength at said large viewing angle is close to a peak emitted wavelength from said microcavity at said 0°

viewing angle.

25. The OLED device of claim 22 wherein at a large viewing angle where said microcavity is amplifying a shorter wavelength with insignificant intensity, said resonant wavelength is different than a peak emitted wavelength from said microcavity at said large viewing angle.

26. The OLED device of claim 22 wherein said color change begins to occur when a wavelength emits a different hue than that of said peak emitted wavelength from said microcavity at a 0°

viewing angle.

27. The OLED device of claim 23 wherein said intensity of said luminance components at wavelengths shorter than said resonant optical length of said microcavity at 0°

viewing angle minus 20 nm is less than 5% of an intensity of a peak emitted wavelength of said material.

28. A method to minimize or eliminate color change in the light emitted from a microcavity OLED device at a large viewing angle, said device includes a microcavity and an emissive layer, said method comprising:

if a resonant wavelength at said large viewing angle is a wavelength shorter than a resonant optical length of said microcavity at 0°

viewing angle minus 20 nm, then amplifying, using said microcavity, insignificant emission intensities of said emissive layer; and

if said resonant wavelength at said large viewing angle is a wavelength longer than a resonant optical length of said microcavity at 0°

viewing angle minus 20 nm, then amplifying, using said microcavity, significant emission intensities of said emissive layer.

29. The method of claim 28 wherein said insignificant emission intensity is an intensity that is less than 5% of an emission intensity of a peak emitted wavelength of said emissive layer.