Rules For Efficient Light Sources Using Phosphor Converted Leds

• US 20080135860A1
• Filed: 02/22/2005
• Published: 06/12/2008
• Est. Priority Date: 02/20/2004
• Status: Active Grant

• Current Assignee: Alok Mani Srivastava, Anant A. Setlur, Charles Adrian Becker, Holly Ann Comanzo, Josesph Shiang, Stanton Earl Weaver, Steven Duclos, Thomas Soules
• Original Assignee: Alok Mani Srivastava, Anant A. Setlur, Charles Adrian Becker, Holly Ann Comanzo, Josesph Shiang, Stanton Earl Weaver, Steven Duclos, Thomas Soules
• Inventors: Shiang, Josesph, Soules, Thomas, Becker, Charles Adrian, Srivastava, Alok Mani, Weaver, Stanton Earl, Comanzo, Holly Ann, Duclos, Steven, Setlur, Anant A.
• Granted Patent: US 7,884,382 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/616 with alkali or alkaline earth metals
• CPC Class Codes: C09K 11/7731 with alkaline earth metals
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C09K 11/7738 with alkaline earth metals
• CPC Class Codes: C09K 11/7739 with halogens
• CPC Class Codes: C09K 11/774 Borates
• CPC Class Codes: C09K 11/7768 with alkaline earth metals
• CPC Class Codes: C09K 11/7775 Germanates
• CPC Class Codes: C09K 11/778 Borates
• CPC Class Codes: C09K 11/7786 with alkaline earth metals
• CPC Class Codes: C09K 11/7787 Oxides C09K11/7785 takes precedence
• CPC Class Codes: C09K 11/7794 Vanadates; Chromates; Molybdates; Tungstates
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body

Abstract

An LED lamp including an LED and one or more phosphors, wherein for each phosphor, a figure of merit (FOM) defined as the product of (incident LED flux)×(excitation cross-section of the phosphor)×(phosphor material decay time) is less than 0.3. Such an arrangement provides a light emitting device with improved lumen output and color stability over a range of drive currents.

Claims

1. A light emitting device comprising an LED and one or more phosphor materials, wherein for each phosphor material, the product of (incident LED flux)×

(excitation cross-section of the phosphor)×

(phosphor material decay time) is less than 0.3.

2. The device of claim 1, wherein the LED is comprised of a semiconductor material.

3. The device of claim 1, wherein the LED emits light between 350 and 490 nm.

4. The device of claim 1, wherein the product is less than 0.1.

5. The device of claim 1, wherein the phosphor material provides Eu^2+—

Mn²⁺ energy transfer.

6. The device of claim 1, wherein said phosphor material includes at least one of Eu³⁺, Tb³⁺, Mn⁴⁺, Pr³⁺, Eu²⁺, or Ce³⁺.

7. The device of claim 6, including a first phosphor material dispersed farther from the LED chip than the phosphor of claim 6 and wherein said first phosphor material has a slower decay time than the phosphor of claim 6.

8. The device of claim 1, including at least one phosphor with a faster decay time placed closer to the LED chip and at least one phosphor having a slower decay time further fom the LED chip.

9. The device of claim 1, wherein said phosphor material is positioned remote to the LED.

10. The device of claim 1, including a first phosphor material having a fast decay time positioned in a first layer adjacent to the LED and a phosphor material in a second layer having a longer decay time and positioned remote to the LED.

11. The device of claim 10 having three or more phosphor layers.

12. The device of claim 11, wherein each phosphor layer in a direction outward from the LED has a longer decay time.

13. The device of claim 10 wherein said phosphor layers are comprised of one or more phosphor.

14. The device of claim 1 including a phosphor with a decay time less than about 1 ms and positioned relatively closer to the LED and a phosphor positioned farther away from the LED and having a decay time of greater than about 3 ms.

15. The device of claim 8, wherein Eu²⁺—

Mn²⁺ phosphors are used in the layers farther from the LED.

16. A method for producing a phosphor conversion LED lamp, the method comprising the steps of providing an LED chip and subsequently depositing one or more phosphor materials over the LED chip, wherein the phosphor materials are selected and deposited such that for each phosphor material, the product of (incident LED flux)×

(excitation cross-section of the phosphor)×

(phosphor material decay time) is less than 0.3.