Organic electroluminescent device with plural microcavities

{
  "publication_number": "US5949187A",
  "country": "US",
  "kind": "A",
  "title": "Organic electroluminescent device with plural microcavities",
  "abstract": "An OED with a first microcavity including a first transparent spacer positioned adjacent the diode light output and a first mirror stack positioned on the first spacer to reflect light back into the OED and to define an optical length of the first microcavity. The optical length of the first microcavity being such that light emitted from the first microcavity has a first spectrum. A second microcavity including a second transparent spacer positioned adjacent the first microcavity and a second mirror stack positioned on the second spacer to reflect light toward the first microcavity and to define an optical length of the second microcavity. The optical length of the second microcavity being such that light emitted from the second microcavity has a second spectrum. Additional microcavities can be placed in the structure to further enhance and alter the light spectrum.",
  "claims": [
    "1. An organic light emitting device comprising a first microcavity including an organic light emitting diode and a first mirror, having a light output with a light spectrum and one or more additional microcavities, each additional microcavity including a mirror positioned in tandem with the light output to successively alter the light spectrum.",
    "2. An organic light emitting device as claimed in claim 1 wherein the optical length of the first microcavity is constructed to shift a peak of the light spectrum toward a blue side of the light spectrum.",
    "3. An organic light emitting device as claimed in claim 1 wherein the optical length of the first microcavity is constructed to shift a peak of the light spectrum toward a red side of the light spectrum.",
    "4. An organic light emitting device as claimed in claim 1 wherein each of the first and additional microcavities has a substantially equal optical length.",
    "5. An organic light emitting device comprising: an organic light emitting diode including a diode light output; a first microcavity including a first plurality of layers of material having different indexes of refraction such that the first plurality of layers operates as a first mirror stack, the first plurality of layers being positioned in spaced relationship from the diode light output to reflect light from the diode light output toward the organic light emitting diode and to cooperate with the organic light emitting diode to define an optical length of the first microcavity, the first plurality of layers further defining a first microcavity light output, and the optical length of the first microcavity being such that light emitted from the first microcavity light output has a first spectrum; and a second microcavity including a second plurality of layers of material having different indexes of refraction such that the second plurality of layers operates as a second mirror stack, the second plurality of layers being positioned in spaced relationship from the first microcavity light output to reflect light from the first microcavity light output toward the first microcavity and to define an optical length of the second microcavity, the second plurality of layers further defining a second microcavity light output, and the optical length of the second microcavity being such that light emitted from the second microcavity light output has a second spectrum.",
    "6. An organic light emitting device as claimed in claim 5 wherein the organic light emitting diode includes an organic light emitting zone sandwiched between first and second electrical contacts with the first electrical contact being transparent to emitted light and defining the diode light output.",
    "7. An organic light emitting device as claimed in claim 6 wherein the second electrical contact of the organic light emitting diode includes metal, the metal forming a reflective surface in the organic light emitting diode opposite the diode light output.",
    "8. An organic light emitting device as claimed in claim 5 wherein the first and second pluralities of layers of material each include pairs of layers, one layer of each pair having a first index of refraction and another layer of each pair having a second index of refraction lower than the first index of refraction with each pair of layers cooperating to reflect light.",
    "9. An organic light emitting device as claimed in claim 8 wherein each pair of layers of the first and second pluralities of layers defines a partial mirror with an operating thickness of an integer multiple of one half wavelength of the emitted light.",
    "10. An organic light emitting device as claimed in claim 8 wherein each pair of layers includes a layer of silicon dioxide and a layer of titanium dioxide.",
    "11. An organic light emitting device as claimed in claim 5 wherein the first plurality of layers of material is constructed with a first reflectivity to light from the first transparent spacer and a second reflectivity to light from the second transparent spacer, the first reflectivity being lower than the second reflectivity.",
    "12. An organic light emitting device as claimed in claim 11 wherein the first plurality of layers of material includes a final layer adjacent the second transparent spacer formed to increase the second reflectivity above the first reflectivity.",
    "13. An organic light emitting device as claimed in claim 11 wherein the second reflectivity is at least 0.1 greater than the first reflectivity.",
    "14. An organic light emitting device as claimed in claim 5 wherein the optical length of the first microcavity is constructed to shift a peak of the first spectrum toward a blue side of the light spectrum.",
    "15. An organic light emitting device as claimed in claim 5 wherein the optical length of the first microcavity is constructed to shift a peak of the first spectrum toward a red side of the light spectrum.",
    "16. An organic light emitting device as claimed in claim 5 including additional microcavities each including a transparent spacer with a plurality of layers of material having different indexes of refraction positioned thereon so as to operate as a mirror stack, each additional microcavity being positioned in tandem with a previous microcavity to provide a light output with a different spectrum.",
    "17. An organic light emitting device as claimed in claim 16 wherein the first and second microcavities and each additional microcavity all have a substantially equal optical length.",
    "18. An organic light emitting device comprising: an organic light emitting diode including an organic light emitting zone sandwiched between first and second electrical contacts with the first electrical contact being transparent to emitted light and defining the diode light output; a first microcavity including a first transparent spacer positioned adjacent the diode light output and a first plurality of layers of dielectric material having different indexes of refraction such that the first plurality of layers operates as a first mirror stack, the first plurality of layers being positioned on the first transparent spacer so as to reflect light toward the organic light emitting diode and to cooperate with the first transparent spacer and the organic light emitting diode to define an optical length of the first microcavity, the first plurality of layers further defining a first microcavity light output, the optical length of the first microcavity being such that light emitted from the first microcavity light output has a first spectrum; a second microcavity including a second transparent spacer positioned adjacent the first microcavity light output and a second plurality of layers of dielectric material having different indexes of refraction such that the second plurality of layers operates as a second mirror stack, the second plurality of layers being positioned on the second spacer so as to reflect light toward the first microcavity and to define an optical length of the second microcavity, the second plurality of layers further defining a second microcavity light output, the optical length of the second microcavity being such that light emitted from the second microcavity light output has a second spectrum; and a transparent substrate supporting the second microcavity and defining a device light output.",
    "19. An organic light emitting device as claimed in claim 18 wherein the first and second pluralities of layers of material each include pairs of layers, one layer of each pair having a first index of refraction and another layer of each pair having a second index of refraction lower than the first index of refraction with each pair of layers cooperating to reflect light.",
    "20. An organic light emitting device as claimed in claim 19 wherein each pair of layers defines a partial mirror with an operating thickness of an integer multiple of one half wavelength of the emitted light.",
    "21. An organic light emitting device as claimed in claim 19 wherein each pair of layers includes a layer of silicon dioxide and a layer of titanium dioxide.",
    "22. An organic light emitting device as claimed in claim 18 wherein the first plurality of layers of material is constructed with a first reflectivity to light from the first transparent spacer and a second reflectivity to light from the second transparent spacer, the first reflectivity being lower than the second reflectivity.",
    "23. An organic light emitting device as claimed in claim 22 wherein the first plurality of layers of material includes a final layer adjacent the second transparent spacer formed to increase the second reflectivity above the first reflectivity.",
    "24. An organic light emitting device as claimed in claim 22 wherein the second reflectivity is at least 0.1 greater than the first reflectivity.",
    "25. An organic light emitting device as claimed in claim 18 wherein the optical length of the first microcavity is constructed to shift a peak of the first spectrum toward a blue side of the light spectrum.",
    "26. An organic light emitting device as claimed in claim 18 wherein the optical length of the first microcavity is constructed to shift a peak of the first spectrum toward a red side of the light spectrum.",
    "27. An organic light emitting device as claimed in claim 18 including additional microcavities each including a transparent spacer with a plurality of layers of material having different indexes of refraction positioned thereon so as to operate as a mirror stack, each additional microcavity being positioned in tandem with a previous microcavity to provide a light output with a different spectrum.",
    "28. An light emitting device comprising: a light emitting diode including a diode light output; a first microcavity including a first transparent spacer positioned adjacent the diode light output and a first plurality of pairs of layers of material having different indexes of refraction such that each pair of layers of the first plurality of pairs of layers operates as a partial mirror, the first plurality of pairs of layers being positioned on the first transparent spacer so as to reflect light toward the light emitting diode and to cooperate with the first transparent spacer and the light emitting diode to define an optical length of the first microcavity, the first plurality of pairs of layers further defining a first microcavity light output, the optical length of the first microcavity being such that light emitted from the first microcavity light output has a first spectrum; and a second microcavity including a second transparent spacer positioned adjacent the first microcavity light output and a second plurality of pairs of layers of material having different indexes of refraction such that each pair of layers of the second plurality of pairs of layers operates as a partial mirror, the second plurality of pairs of layers being positioned on the second spacer so as to reflect light toward the first microcavity and to define an optical length of the second microcavity, the second plurality of pairs of layers further defining a second microcavity light output, the optical length of the second microcavity being such that light emitted from the second microcavity light output has a second spectrum.",
    "29. An light emitting device as claimed in claim 28 wherein the first and second transparent spacers and the first and second pluralities of pairs of layers are formed of dielectric material.",
    "30. An light emitting device as claimed in claim 28 wherein the first and second transparent spacers are formed of one of silicon nitride and silicon dioxide."
  ],
  "description_excerpt": "The present invention pertains to light emitting diodes and more specifically to apparatus for enhancing the power and/or color of the light output of organic light emitting diodes.\n\nLight emitting diode (LED) arrays are becoming more popular as an image source in both direct view and virtual image displays. One reason for this is the fact that LEDs are capable of generating relatively high amounts of light (high luminance), which means that displays incorporating LED arrays can be used in a greater variety of ambient conditions. For example, reflective liquid crystal displays (LCD's) can only be used in high ambient light conditions because they derive their light from the ambient light, i.e. the ambient light is reflected by the LCDs. Some transflective LCDs are designed to operate in a transmissive mode and incorporate a backlighting arrangement for use when ambient light is insufficient. In addition, transflective displays have a certain visual aspect and some users prefer a bright emissive display. However, these types of displays are generally too large for practical use in very small devices, such as portable electronic devices.\n\nOrganic electroluminescent device (OED) arrays are emerging as a potentially viable design choice for use in small products, especially small portable electronic devices, such as pagers, cellular and portable telephones, two-way radios, data banks, etc. OED arrays are capable of generating sufficient light for use in displays under a variety of ambient light conditions (from little or no ambient light to bright ambient light).",
  "cpc": [
    "H10K 50/125",
    "H10K 50/852"
  ],
  "ipc": [
    "H10K 50/852"
  ],
  "assignees": [
    "Motorola Inc"
  ],
  "inventors": [
    "Ji-Hai Xu",
    "Rong-Ting Huang",
    "Franky So"
  ],
  "filing_date": "1997-07-29",
  "publication_date": "1999-09-07",
  "grant_date": "1999-09-07",
  "priority_date": "1997-07-29",
  "application_number": "US-90238797-A",
  "family_id": "25415797",
  "cited_by_count": 124,
  "citations": [
    "US5405710A",
    "EP0683623A1",
    "US5478658A"
  ]
}