Display devices using feedback enhanced light emitting diode

• US 20030214691A1
• Filed: 05/08/2003
• Published: 11/20/2003
• Est. Priority Date: 05/08/2002
• Status: Active Grant

• Current Assignee: Red Bank Technologies LLC
• Original Assignee: Zeolux Corporation
• Inventors: Koch, Gene C., Magno, John N.
• Granted Patent: US 9,129,552 B2
• Time in Patent Office: Days
• US Class Current: 359/196
• CPC Class Codes: G09G 3/2803 Display of gradations G09G3/288 takes precedence
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: H01L 33/465 with a resonant cavity structure
• CPC Class Codes: H01S 3/08059 Constructional details of the reflector, e.g. shape mirrors in general G02B5/08; mountings for mirrors G02B7/18
• CPC Class Codes: H01S 3/1065 using liquid crystals
• CPC Class Codes: H01S 3/1686 Liquid crystal active layer
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• CPC Class Codes: H01S 5/36 comprising organic materials
• CPC Class Codes: H10K 2102/3031 Two-side emission, e.g. transparent OLEDs [TOLED]
• CPC Class Codes: H10K 50/816 Multilayers, e.g. transparent multilayers
• CPC Class Codes: H10K 50/828 Transparent cathodes, e.g. comprising thin metal layers
• CPC Class Codes: H10K 50/8426 Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 50/856 comprising reflective means
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/1201 Manufacture or treatment
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/17 : Passive-matrix OLED displays
• CPC Class Codes: H10K 59/35 : comprising red-green-blue [RGB] subpixels
• CPC Class Codes: H10K 59/65 : OLEDs integrated with inorganic image sensors
• CPC Class Codes: H10K 71/00 : Manufacture or treatment specially adapted for the organic devices covered by this subclass

Abstract

Display devices using feedback-enhanced light emitting diodes are disclosed. The display devices include but are not limited to active and passive matrix displays and projection displays. A light emissive element disposed between feedback elements is used as light emitting element in the display devices. The light emissive element may include organic or non-organic material. The feedback elements coupled to an emissive element allow the emissive element to emit collimated light by stimulated emission. In one aspect, feedback elements that provide this function include, but are not limited to, holographic reflectors with refractive index variations that are continuous.

Claims

1. A display device, comprising:

a first feedback layer adapted to receive and reflect light;

one or more first electrode strips formed over the first feedback layer;

one or more semiconducting layers formed over the first electrode strips, at least one of the one or more semiconducting layers comprising at least a luminescent material;

one or more second electrode strips formed over the luminescent material the second electrode strips being formed such that they overlay one or more of the first electrode strips, wherein an area where the first electrode strip and the second electrode strip overlap comprises a segment area capable of being driven via the first electrode strips and the second electrode strips;

a second feedback layer adapted to receive and reflect light disposed over the one or more second electrode strips; and

an imaging element disposed proximate to one of the first feedback layer and the second feedback layer.

2. The device of claim 1, wherein the overlay areas of the first electrode strips and the second electrode strips comprise at least a rectilinear matrix of display pixels.

3. The device of claim 1, wherein one or both of the first feedback layer and the second feedback layer has a refractive index profile that varies at least in part periodically along an axis normal or substantially normal to a plane of a respective feedback layer.

4. The device of claim 3, wherein one or both of the first feedback layer and the second feedback layer that have substantially periodically varying refractive index profiles have at least in part continuously varying refractive index profiles.

5. The device of claim 1, wherein one or both of the first feedback layer and the second feedback layer comprise at least a layer with a photonic crystal structure.

6. The device of claim 1, wherein a distance between the first feedback layer and the second feedback layer is such that the space between the feedback layers constitutes a cavity in which light of one or more desired wavelengths constructively interfere.

7. The device of claim 1, wherein light reflected by one or both of the first feedback layer and the second feedback layer stimulates emission of light from the one or more layers of luminescent material.

8. The device of claim 7, wherein the stimulated emission of light results in substantial collimation of light emitted by the device.

9. The device of claim 7, wherein the stimulated emission of light results in laser action.

10. The device of claim 1, wherein the luminescent material comprises an organic luminescent material.

11. The device of claim 10, wherein the organic luminescent material comprises a polymeric material.

12. The device of claim 10, wherein the organic luminescent material comprises an oligomeric material.

13. The device of claim 10, wherein the organic luminescent material is photo-cross-linked.

14. The device of claim 1, wherein the luminescent material comprises an organometallic material.

15. The device of claim 1, wherein the luminescent material comprises an inorganic material.

16. The device of claim 1, wherein the luminescent material comprises an inorganic and organic composite material.

17. The device of claim 3, wherein one or both of the first feedback layer and the second feedback layer comprises at least a layer of holographic recording material.

18. The device of claim 3, wherein one or both of the first and the second feedback layers comprises at least a layer of holographic recording material disposed on a substrate.

19. The device of claim 5, wherein one or both of the photonic crystal structures include one-dimensional, two-dimensional, or three-dimensional photonic crystal structures or combination thereof.

20. The device of claim 3, wherein one or both of the first feedback layer and the second feedback layer comprise at least a layer of holographic recording material with a recorded plane wave interference pattern.

21. The device of claim 1, wherein the luminescent material comprises pure material, a solid solution, an alloy, or inhomogeneous mixture, or combination thereof.

22. The device of claim 1, wherein the luminescent material is patterned into areas that are spatially registered with the segment areas.

23. The device of claim 22, wherein the patterned areas are discrete patterned areas.

24. The device of claim 23, wherein the discrete patterned areas comprise two or more luminescent material compositions, each of the discrete patterned areas comprising one of the two or more luminescent material compositions and each of the two or more luminescent material compositions emitting a different spectral band of visible light.

25. The device of claim 3, wherein a spectral reflection band of one or both of the feedback layers substantially overlaps a spectral emission band or bands of the luminescent material.

26. The device of claim 25, wherein one or both of the feedback layers are patterned into areas such that each area has one of two or more periods of refractive index alternation corresponding to different spectral reflection bands representing different colors of reflected light.

27. The device of claim 26, wherein the areas are discrete areas.

28. The device of claim 26, wherein both of the feedback layers have substantially periodic refractive index profiles.

29. The device of claim 28, wherein the corresponding areas in one feedback layer are of substantially the same shape and size as those in the other feedback layer and are spatially registered on them.

30. The device of claim 28, wherein the corresponding areas in the two feedback layers have spectral reflection bands that substantially overlap each other.

31. The device of claim 28, wherein the patterned areas of the luminescent material comprise two or more luminescent materials, each patterned area comprising one of the two or more luminescent materials, each of the luminescent materials emitting a different spectral band of visible light.

32. The device of claim 31, wherein the patterned areas of the luminescent material are discrete patterned areas.

33. The device of claim 31, wherein the patterned areas of the luminescent material correspond to the patterned areas in one or both of the feedback layers.

34. The device of claim 33, wherein the patterned areas of the luminescent material are of substantially the same shape and size as the corresponding patterned areas in the feedback layers or of the combination of one or more of the corresponding patterned areas in the feedback layers.

35. The device of claim 34, wherein spectral emission bands of the patterned areas in the luminescent material at least partially overlap the spectral reflectance bands of corresponding patterned areas in one or both of the feedback layers.

36. The device of claim 2, wherein the luminescent material is patterned into areas, the patterned areas being spatially registered with the matrix of pixels.

37. The device of claim 36, wherein the patterned areas comprise discrete patterned areas.

38. The device of claim 36, wherein the luminescent material is photo-cross-linkable and patterned by a patterned exposure.

39. The device of claim 36, wherein the patterned areas of the luminescent material comprise two or more luminescent materials, each patterned area comprising one of the two or more luminescent materials, each of the two or more luminescent materials emitting a different spectral band of visible light.

40. The device of claim 3, wherein a spectral reflection band of one or both of the feedback layers substantially overlap the spectral emission band or bands of the luminescent material,

and wherein the overlay areas of the first and second electrode strips comprise a rectilinear matrix of display pixels.

41. The device of claim 40, wherein both of the feedback layers have substantially periodic refractive index profiles and are patterned into areas, each area having one of two or more periods of refractive index alternations corresponding to different spectral reflection bands,

the corresponding areas in both the feedback layers being of substantially the same shape and size and map onto the rectilinear array of pixels in the luminescent material,

the corresponding areas in the feedback layers having spectral reflection bands that substantially overlap each other.

42. The device of claim 40, wherein the pixel areas of the material in the rectilinear pixel matrix comprise two or more luminescent materials, each pixel area comprising one of the two or more luminescent materials, each of the two or more luminescent materials emitting a different spectral band of visible light,

the pixel areas of the luminescent material corresponding to the patterned areas in one or both of the feedback layers,

the pixel areas in the luminescent material being of substantially the same shape and size as the corresponding areas in the feedback layers or of the combination of one or more of the corresponding areas in the feedback layers,

a spectral emission bands of the patterned areas in the material at least partially overlapping a spectral reflectance bands of corresponding areas in the feedback layers.

43. The device of claim 40, wherein one or both of the feedback layers that have substantially periodic refractive index profiles are patterned into discrete pixel areas such that each pixel area has a period of refractive index alternation corresponding to a spectral reflection band corresponding to one of red, green, and blue reflected light,

and the red, green, and blue light emitting pixel areas alternate forming a dot-matrix image source capable of displaying full-color graphics.

44. The device of claim 42, wherein the patterned pixel areas in both the feedback layers and the luminescent material are configured to emit one of red, green, and blue light,

the red, green, and blue light emitting pixel areas arranged alternatingly and forming a dot-matrix image source capable of displaying full-color graphics.

45. The device of claim 43, wherein the alternating red, green, and blue pixel areas combine to form red, green, and blue vertical stripes across the device.

46. The device of claim 43, wherein the alternating red, green and blue pixel areas are clustered to form color triads across the device.

47. The device of claim 44, wherein the luminescent material whose spectral emission band is optimized for blue wavelengths of light comprises parahexaphenyl.

48. The device of claim 43, wherein the luminescent material whose spectral emission is optimized for green wavelengths of light comprises tris-(8-hydroxyquinoline) aluminum.

49. The device of claim 43, wherein the luminescent material whose spectral emission is optimized for red wavelengths of light comprises 5,10,14,20-tetraphenylporphine.

50. The device of claim 1, wherein the first electrode strips comprise a transparent, high work function material that functions as an anode injecting holes into the adjacent semiconducting layer.

51. The device of claim 50 wherein the transparent, high work function material comprises indium-tin oxide.

52. The device of claim 1, wherein the second electrode strips comprise a low work function material that functions as a cathode injecting electrons into the adjacent semiconducting layer.

53. The device of claim 1, wherein the second electrode strips comprise a highly reflective metal and serves as the second feedback layer.

54. The device of claim 1, wherein the second electrode strips comprise a transparent material.

55. The device of claim 1, wherein the second electrode strips comprise a first, very thin metal layer adjacent to the semiconducting layer and a second thicker layer comprising a transparent conductive material.

56. The device of claim 55, wherein the transparent conductive material comprises indium-tin oxide.

57. The device of claim 1, wherein light emitted by the device occupies two or more light propagation modes.

58. The device of claim 1, wherein one or both of the first feedback layer and the second feedback layer comprises refractive index profiles that have superimposed multiple periodic spatial frequencies of variation.

59. The device of claim 1, wherein both the first feedback layer and the second feedback layer transmit no light at a peak wavelength of their spectral reflection bands and the light emissive material radiates light into band-edge laser modes.

60. The device of claim 1, further including a transparent cover disposed between the second electrode strips and the second feedback layer.

61. The device of claim 1, further including a substrate over which the first feedback layer is disposed.

62. The device of claim 61, wherein the substrate comprises a glass substrate.

63. The device of claim 61, wherein the substrate comprises one or more of a flexible plastic substrate, a metal substrate, a semiconductor material.

64. The device of claim 1, further comprising a hole transport layer disposed between the luminescent material and the first electrode strips.

65. The device of claim 64, further comprising a hole injection layer disposed between the hole transport layer and the first electrode strips.

66. The device of claim 1, further comprising an electron transport layer disposed between the luminescent material and the second electrode strips.

67. The device of claim 66, further comprising an electron injection layer disposed between the electron transport layer and the second electrode strips.

68. The device of claim 57, further comprising a hole transport layer disposed between the luminescent material and the second electrode strips.

69. The device of claim 68, further comprising a hole injection layer disposed between the hole transport layer and the second electrode strips.

70. The device of claim 57, further comprising an electron transport layer disposed between the luminescent material and the first electrode strips.

71. The device of claim 57, further comprising an electron injection layer disposed between the electron transport layer and the first electrode strips.

72. The device of claim 2, wherein each of the pixels in the rectilinear matrix has drive circuit associated with it.

73. The device of claim 72, wherein each of the pixel drive circuits addresses a single pixel,

each pixel having the electrode strip that functions as its anode electrically isolated from all of the other pixel anodes,

all of the pixel electrode strips that function as cathodes being connected in common.

74. The device of claim 72, wherein each pixel drive circuit comprises two or more thin film transistors.

75. The device of claim 74, wherein a first thin film transistor has its drain electrically connected to one of the first electrode strips and the second electrode strips of a single pixel that functions as an anode, and its source electrically connected to a current source bus line.

76. The device of claim 75, wherein a second thin film transistor has its drain electrically connected to a gate of the first thin film transistor, its source connected to a data bus and its gate connected to a row select line.

77. The device of claim 72, wherein the first feedback layer for a pixel is shaped as a mesa covering at least part of the pixel drive circuit and at least part of the substrate.

78. The device of claim 77, wherein a pixel anode to thin film transistor interconnection is formed on a side of the mesa.

79. The device of claim 77, wherein the pixel drive circuits are formed on a raised ribs formed on the substrate.

105. The device of claim 35, wherein one or more of the luminescent materials has a broad spectral band emission that can be used in the domains or areas of the luminescent material located corresponding to domains or areas in the first feedback layer or the second feedback layer or both the first feedback layer and the second feedback layer that have plane wave interference patterns corresponding to different wavelengths of light.

106. The device of claim 42, wherein one or more of the luminescent materials has a broad spectral band emission that can be used in the areas of the luminescent material located corresponding to areas in the first feedback layer or the second feedback layer or both the first feedback layer and the second feedback layer that have plane wave interference patterns corresponding to different wavelengths of light.

107. The device of claim 1, wherein the luminescent material comprises liquid crystalline material.

108. The device of claim 1, wherein the luminescent material comprises cross-linked material.

109. The device of claim 1, wherein the structure comprising the electrodes, semiconductor and light emissive layers is formed in a defect in a continuous photonic crystal formed by the first feedback layer and the second feedback layer.

110. The device of claim 109, wherein the defect comprises a phase-slip in a spatial phase of the photonic crystal of less than one wavelength.

111. The device of claim 109, wherein the light emitted from the layer of light emissive material emanates into a defect mode.

112. The device of claim 109, wherein the photonic crystal structure includes one-dimensional, two-dimensional, or three-dimensional photonic crystal structures or combinations thereof.

113. The device of claim 1, wherein the imaging element comprises a projection lens.

114. The device of claim 1, wherein the imaging element comprises a rear projection screen.

115. The device of claim 113, wherein the projection lens comprises a compound lens.

116. The device of claim 1, wherein all light emitted by the device occupies a single light propagation mode.

117. The device of claim 116, wherein spacing between the first feedback layer and the second feedback layer is equivalent to λ

/2 excluding phase shifts due to reflection, λ

being a wavelength of the light in the single light propagation mode.

80. A method of fabricating a display device, comprising:

forming pixel drive circuits on a substrate;

forming a first feedback layer having continuously varying refractive index profile on the substrate with pixel drive circuits;

forming a first conductive layer on the first feedback layer;

patterning the first conductive layer into first electrodes;

forming interconnections from the pixel drive circuits to the first electrodes;

forming a light emitting diode structure comprising at least one emissive layer on the first feedback layer and first electrodes;

forming a second conductive layer on the light emitting diode structure;

patterning the second conductive layer into second electrodes; and

forming a second feedback layer over the light emitting diode structure.

81. The method of claim 80, wherein the pixel drive circuits each comprise two or more thin film transistors.

82. The method of claim 80, wherein one or both of the first and the second feedback layers has a refractive index profile that varies substantially periodically along an axis normal to a plane of the respective feedback layer.

83. The method of claim 80, wherein one or both of the first and the second feedback layers comprise holographic recording material.

84. The method of claim 83, wherein one or both of the first and the second feedback layers comprise holographic recording material containing a plane wave interference pattern.

85. The method of claim 80, wherein the first feedback layer includes a layer of holographic material patterned with areas that reflect red, green, and blue wavelength bands of light.

86. The method of claim 80, wherein the at least one emissive layer comprises an organic light emitting material.

87. The method of claim 80, wherein the pixel drive circuits are formed on ribs formed on the substrate.

88. A method of fabricating a display device, comprising:

forming a substrate;

forming a first feedback layer having a continuously varying refractive index profile on the substrate;

forming one or more first electrode strips on the first feedback layer;

forming an OLED device comprising at least one layer of emissive material over the first electrode strips;

forming one or more second electrode strips over the OLED device overlaying the first electrode strips, wherein areas of the OLED device where the first electrode strip and the second electrode strip overlap form pixel areas capable of being driven via the first electrode strips and the second electrode strips; and

forming a second feedback layer over the one or more second electrode strips.

89. The method of claim 88, wherein one or both of the first and the second feedback layers comprise at least a layer of holographic recording material.

90. The method of claim 88, wherein one or both of the first and the second feedback layers comprise at least a layer of holographic recording material containing a plane wave interference pattern.

91. A display device, comprising:

a first feedback layer;

a second feedback layer;

an luminescent device comprising at least one layer of semiconductor material disposed between the first feedback layer and the second feedback layer, the at least one layer of the semiconducting material comprising an luminescent material;

a projection lens disposed proximate to a light emitting portion of the second feedback layer.

92. The device of claim 91, wherein one or both of the first and the second feedback layers comprises holographic recording material.

93. The device of claim 91, wherein one or both of the first and the second feedback layers comprises holographic recording material patterned with red, green, and blue wavelength interference patterns.

104. The device of claim 91, wherein the luminescent material comprises luminescent material composition.

94. A display device, comprising:

a first feedback layer;

a second feedback layer;

an luminescent device comprising at least one layer of semiconductor material disposed between the first feedback layer and the second feedback layer;

the at least one layer of the semiconducting material comprising at least an luminescent material;

a rear projection screen proximate to an emissive surface of the first feedback layer.

95. The device of claim 94, wherein the luminescent device acts as an image source with an image projected with unity magnification on the rear projection screen.

96. The device of claim 94, wherein the rear projection screen is bonded directly to an outside surface of the first feedback layer.

97. The device of claim 94, wherein the rear projection screen comprises an array of tapered micro-light guides.

98. The device of claim 94, wherein interstitial areas between the tapered micro-light guides are filled with a black, light absorbing material of lower refractive index than material of the micro-light guides.

99. The device of claim 94, wherein the rear projection screen comprises at least in part of transparent microbeads.

100. The device of claim 99, wherein interstitial areas between the microbeads are filled with a black, light absorbing material of lower refractive index than material of the microbeads.

101. The device of claim 94, wherein the rear projection screen comprises a light diffusing material.

102. The device of claim 94, wherein the rear projection screen comprises microlenslets.

103. The device of claim 94, wherein the luminescent material comprises luminescent material composition.