Solid-state area illumination system

• US 7,838,889 B2
• Filed: 08/10/2007
• Issued: 11/23/2010
• Est. Priority Date: 08/10/2007
• Status: Active Grant

• Current Assignee: Nanoco Technologies Limited (Nanoco Group Plc)
• Original Assignee: Eastman Kodak Company
• Inventors: Cok, Ronald S., Kane, Paul J.
• Primary Examiner(s): Gurley; Lynne A
• Assistant Examiner(s): YUSHINA, GALINA G
• Application Number:
  US11/837,026
• Publication Number:
  US 20090039360A1
• Time in Patent Office: 1,201 Days
• Field of Search: 257/13, 257/14, 257/88, 257/94, 257/79, 257/59, 257/E29.071, 257/E29.069, 257/17, 313/506, 313/504, 362/226, 362/227
• US Class Current: 257/79
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/565 with zinc cadmium
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source

Abstract

A solid-state area illumination system includes multiple LED devices, each LED device is formed on a separate substrate and each LED device emits differently colored light at different angles relative to the substrate. The peak frequencies of each color of light differ by at least the smallest of the full width half maximums of the frequency distributions of emitted light. Also included is a support for positioning each of the LED devices at multiple orientations relative to an area of illumination upon a surface, so that any point within the area of illumination will receive multiple colors of light from more than one of the LED devices at different angles. Each LED device includes one or more light-emitting elements, each light-emitting element having multiple sizes of core/shell quantum-dot emitters formed in a common polycrystalline semiconductor matrix.

Claims

1. A solid-state area illumination system, comprising:

a. a plurality of LED devices, each LED device formed on a separate substrate and each LED device emitting differently colored light at different angles relative to the substrate;

wherein each color of light has a frequency distribution including a peak and full width half maximum and wherein the peak frequencies of each color of light differ by at least the smallest of the full width half maximums of the frequency distributions of emitted light;

b. a support for positioning each of the plurality of LED devices at a plurality of orientations relative to an area of illumination upon a surface, so that any point within the area of illumination will receive multiple colors of light from more than one of the LED devices at different angles;

wherein each LED device comprises one or more light-emitting elements, each light-emitting element including multiple sizes of core/shell quantum-dot emitters formed in a common polycrystalline semiconductor matrix layer, each different size of quantum-dot emitter in each light-emitting element having a peak emission frequency and emission bandwidth, each light-emitting element further including a single succession of parallel layers, the single succession of parallel layers forming different optical microcavities having different respective optical path lengths at different angles with respect to the normal to the surface of the layers in the single succession of layers, wherein an emission bandwidth of each population of quantum-dot emitters in each light-emitting element is tuned to a frequency response of one of the optical microcavities of that light-emitting element.

2. The solid-state area illumination system claimed in claim 1, wherein each optical microcavity includes two electrodes, one reflective, one semi-reflective;

wherein the two electrodes are separated by an inorganic semiconductor material having an index of refraction.

3. The solid-state area illumination system claimed in claim 2, wherein each optical microcavity is tuned for a predetermined peak emission frequency and emission bandwidth by the LED device, by adjusting the separation of the reflective electrode and the semi-reflective electrode and selecting predetermined values for the indices of refraction of the intervening layers.

4. The solid-state area illumination system claimed in claim 3, wherein the emission of the predetermined center emission frequency and emission bandwidth of the LED device is further accomplished by selecting a predetermined size distribution of quantum dots.

5. The solid-state area illumination system of claim 1, wherein the support is a chandelier, a table lamp, or a floor lamp.

6. The solid-state area illumination system of claim 1, wherein the illuminated area is a floor, wall, ceiling, or item of furniture.

7. The solid-state area illumination system of claim 1, wherein at least one substrate is a rigid planar substrate.

8. The solid-state area illumination system of claim 1, wherein at least one substrate is flexible.

9. The solid-state area illumination system of claim 1, wherein at least one LED device comprises a transparent substrate and transparent cover and light is emitted from both sides of the LED device.

10. The solid-state area illumination system of claim 1, wherein the LED devices emit a single color of light in a direction normal to the surface of the substrate.

11. The solid-state area illumination system of claim 10, wherein the single color of light emitted in a direction normal to the surface of the substrate is red, green, blue, yellow or cyan.

12. The solid-state area illumination system of claim 1, wherein at least one LED device is a top-emitting device.

13. The solid-state area illumination system of claim 1, wherein at least one LED device is a bottom-emitting device.

14. The solid-state area illumination system of claim 1, wherein at least two LED devices have substrates that are in a common plane.

15. The solid-state area illumination system of claim 1, wherein at least two LED devices have substrates that are in different planes.

16. A method of forming a solid-state area illumination system, comprising the steps of:

a. forming multiple sizes of core/shell quantum-dot emitters in a common polycrystalline semiconductor matrix layer, each different size of quantum-dot emitter having a peak emission frequency and emission bandwidth;

b. forming a plurality of light-emitting elements, each light-emitting element including a single succession of parallel layers, the single succession of parallel layers forming different optical microcavities having different respective optical path lengths at different angles with respect to the normal to the surface of the layers in the single succession of lavers, the single succession of layers including an emissive layer containing a population of quantum-dot emitters of two or more sizes, wherein an emission bandwidth of each population of quantum-dot emitters in each light-emitting element is tuned to a frequency response of the optical microcavity of that light-emitting element;

c. forming a plurality of LED devices, each LED device comprising one or more light-emitting elements, each device on a separate substrate and each device emitting light at a plurality of angles relative to the substrate, the emitted light have different colored light at different angles; and

d. providing a support positioning each of the plurality of LED devices at a plurality of orientations relative to an area of illumination, said positioning being defined so that any point on any surface within the area of illumination will receive multiple colors of light from more than one of the LED devices.