White light electroluminescent devices with adjustable color temperature

• US 8,629,611 B2
• Filed: 06/25/2010
• Issued: 01/14/2014
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Haase, Michael A.
• Primary Examiner(s): Patel, Vip
• Application Number:
  US13/379,895
• Publication Number:
  US 20120104935A1
• Time in Patent Office: 1,299 Days
• Field of Search: 313/498, 313/499, 313/506, 313/509, 313/512
• US Class Current: 313/499
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• 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 25/0753 the devices being arranged next to each other
• 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 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/207 Diameter ranges
• 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 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/40 Details of LED load circuits

Abstract

Solid state lighting devices include a first luminescent element (612) emitting light having a first spectrum, and a second luminescent element (614) emitting light having a second spectrum. The first luminescent element includes a first electroluminescent element (612a) that emits a first pump light, and a first light converting element (612b) that converts at least some of the first pump light to a first re-emitted light component. The second luminescent element includes a second electroluminescent element (614a) that emits a second pump light, and a second light converting element (614b) that converts at least some second pump light to a second re-emitted light component. The first and/or second light converting element includes a potential well. Light emitted by the first and second luminescent elements combine to provide a device output, which can approximate a Planckian locus over a range of color temperatures and exhibit a color rendering index of at least 60, 70, or 80.

Claims

1. A solid state lighting device, comprising:

a first luminescent element configured to emit light having a first spectral distribution, the first luminescent element comprising;

a first electroluminescent source emitting a first pump light, and

a first light converting element that converts at least some of the first pump light to a first re-emitted light component; and

a second luminescent element configured to emit light having a second spectral distribution, the second luminescent element comprising;

a second electroluminescent source emitting a second pump light, and

a second light converting element that converts at least some of the second pump light to a second re-emitted light component;

wherein at least one of the first and second light converting elements comprises a first semiconductor stack including a first potential well;

wherein the first and second luminescent elements are disposed so that the light emitted by the first and second luminescent elements combine to provide a device output; and

wherein the first and second spectral distributions can be represented by first and second endpoints, respectively, on a line segment on a standard CIE (x,y) color coordinate diagram, the line segment representing a range of possible device outputs for different relative amounts of the light emitted by the first luminescent element and the light emitted by the second luminescent element, at least a portion of the line segment also approximating a Planckian locus at least over a range of color temperatures from 3000K to 5000K.

2. The device of claim 1, wherein the line segment deviates from the Planckian locus by a distance of less than 0.04 on the CIE (x,y) plane over the color temperature range from 3000K to 5000K.

3. The device of claim 1, wherein the possible device outputs represented by the line segment maintain a color rendering index of at least 60 over the color temperature range from 3000K to 5000K.

4. The device of claim 3, wherein the possible device outputs represented by the line segment maintain a color rendering index of at least 80 over the color temperature range from 3000K to 5000K.

5. The device of claim 1, wherein the first pump light has a first peak wavelength λ

_1p and the second pump light has a second peak wavelength λ

_2p, and where λ

_1p is substantially the same as λ

_2p.

6. The device of claim 1, wherein the first and second pump lights each exhibit a peak wavelength in a range from 350 to 500 nm.

7. The device of claim 1, wherein the first and second electroluminescent sources comprise different portions of a unitary semiconductor element.

8. The device of claim 1, wherein the first and second electroluminescent sources comprise distinct semiconductor elements.

9. The device of claim 1, wherein the first light converting element comprises a phosphor, and wherein the second light converting element comprises the first semiconductor stack including the first potential well.

10. The device of claim 9, wherein the phosphor emits yellow light, and the first semiconductor stack emits amber light.

11. The device of claim 10, wherein the second spectral distribution consists essentially of a first emission band having a peak emission between 500 and 600 nm, and a second emission band having a peak emission between 600 and 700 nm.

12. The device of claim 11, wherein the first emission band has a FWHM width of no more than 50 nm, and the second emission band has a FWHM spectral width of no more than 50 nm.

13. The device of claim 12, wherein the possible device outputs represented by the line segment maintain a color rendering index of at least 60 over the color temperature range from 3000K to 5000K.

14. The device of claim 1, wherein the first light converting element comprises the first semiconductor stack, and the second light converting element comprises a second semiconductor stack that includes a second potential well.

15. The device of claim 14, wherein first semiconductor stack includes a third potential well and the second semiconductor stack includes a fourth potential well, and wherein the first, second, third, and fourth potential wells are capable of generating re-emitted light whose peak wavelengths differ from each other by at least 10 nm.

16. The device of claim 15, wherein the first spectral distribution is characterized by a cyan color, and the second spectral distribution is characterized by an amber color.

17. The device of claim 15, wherein the first spectral distribution comprises a first emission band having a peak emission between 400 nm and 500 nm, and a second emission band having a peak emission between 500 nm and 600 nm.

18. The device of claim 17, wherein the second spectral distribution comprises a third emission band having a peak emission between 500 nm and 600 nm, and a fourth emission band having a peak emission between 600 nm and 700 nm.

19. The device of claim 18, wherein the first, second, third, and fourth emission bands each have a FWHM spectral width of no more than 50 nm, and wherein the possible device outputs represented by the line segment maintain a color rendering index of at least 60 over the color temperature range from 3000K to 5000K.

20. The device of claim 19, wherein the possible device outputs represented by the line segment maintain a color rendering index of at least 80 over the color temperature range from 3000K to 5000K.