Electroluminescent devices with color adjustment based on current crowding

• US 8,304,976 B2
• Filed: 06/25/2010
• Issued: 11/06/2012
• Est. Priority Date: 06/30/2009
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Haase, Michael A.
• Primary Examiner(s): Santiago, Mariceli
• Assistant Examiner(s): Zimmerman, Glenn
• Application Number:
  US13/379,933
• Publication Number:
  US 20120091882A1
• Time in Patent Office: 865 Days
• Field of Search: 313/498, 313/504, 313/502, 257/98
• US Class Current: 313/498
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/502 Wavelength conversion materials

Abstract

A lighting system provides a system optical output, such as white light, as a function of an applied electrical signal. The system output can be characterized by a color temperature or other measure that represents the color or output spectrum of the output. The system is designed so that the color temperature changes as a function of the applied electrical signal. The changes in color temperature are at least in part a result of a phenomenon known as “current crowding”.

Claims

1. A lighting system, comprising:

an electroluminescent device adapted to emit light in response to an applied electrical signal; and

a first light modifying material adapted to modify a first portion of the emitted light to provide a first light component;

wherein the lighting system combines the first light component with at least a second light component associated with a second portion of the emitted light to produce a system optical output;

wherein the system optical output has a color temperature that changes based on the applied electrical signal;

wherein the changes in color temperature are a result of substantial current crowding;

wherein the emitted light is emitted from an output surface of the electroluminescent device, and wherein the electroluminescent device is characterized in that a spatial distribution of the emitted light over the output surface changes as a function of the applied electrical signal, the changes in the spatial distribution being at least in part as a result of the current crowding.

2. The system of claim 1, wherein the system optical output is characterized by a relative proportion of the first to the second light component, and wherein the changes in color temperature are associated with changes in the relative proportion.

3. The system of claim 1, wherein the emitted light has an emitted light spectrum and the first light component has a first spectrum different from the emitted light spectrum.

4. The system of claim 3, further comprising a second light modifying material that modifies the second portion of the emitted light to provide the second light component, the second light component having a second spectrum different from the first spectrum and from the emitted light spectrum.

5. The system of claim 4, wherein the first light modifying material covers a first portion of the output surface and the second light modifying material covers a second portion of the output surface.

6. The system of claim 5, further comprising a third light modifying material covering a third portion of the output surface, the third light modifying material being adapted to modify a third portion of the emitted light to provide a third light component that has a third spectrum different from the first, second, and emitted light spectra.

7. The system of claim 3, wherein the first light modifying material covers a first portion of the output surface, wherein a second portion of the output surface is characterized by an absence of any light modifying material, and wherein the second light component has a second spectrum that is substantially the same as the emitted light spectrum.

8. The system of claim 3, wherein the emitted light spectrum has a peak at a wavelength λ

_p and the first spectrum has a peak at a wavelength λ

₁, and wherein λ

₁>

λ

_p.

9. The system of claim 1, wherein the first light modifying material comprises a phosphor.

10. The system of claim 1, wherein the first light modifying material comprises a first re-emitting semiconductor construction that includes a first potential well.

11. The system of claim 10, further comprising a second light modifying material that modifies the second portion of the emitted light to provide the second light component, the second light modifying material comprising a second re-emitting semiconductor construction that includes a second potential well.

12. The system of claim 5, wherein the electroluminescent device includes an electrical contact disposed on the output surface, wherein the first portion of the output surface is disposed proximate the electrical contact, and wherein the second portion of the output surface is spaced apart from the electrical contact.

13. The system of claim 1, wherein the color temperature changes as a function of a magnitude of the applied electrical signal.

14. The system of claim 13, wherein the color temperature increases with increasing magnitude of the applied electrical signal.

15. A lighting system, comprising:

an electroluminescent device adapted to emit light from an output surface in response to an applied electrical current, the electroluminescent device being characterized in that a spatial distribution of the emitted light over the output surface substantially changes as a function of the electrical current as a result of substantial current crowding; and

a first light converting material covering a first portion of the output surface and adapted to convert a first portion of the emitted light to a first light component;

wherein the first light component combines with at least a second light component to provide a system optical output, the second light component being associated with a second portion of the emitted light; and

wherein the first light converting material is spatially distributed such that the changes in the spatial distribution of the emitted light over the output surface produce changes in a color of the system optical output.

16. The system of claim 15, wherein the second light component is not associated with any light converting material.

17. The system of claim 15, further comprising a second light converting material covering a second portion of the output surface, the second light converting material being adapted to convert the second portion of the emitted light to the second light component.

18. The system of claim 15, wherein the electroluminescent device includes an electrical contact disposed on the output surface, wherein the first portion of the output surface is generally proximate the electrical contact, and wherein the output surface includes a second portion generally spaced apart from the electrical contact.

19. The system of claim 15, wherein the system optical output comprises white light, and wherein the changes in the color comprise changes in a color temperature of the system optical output.