Phosphor systems for a white light emitting diode (LED)
View Patent ↗Novel phosphor systems for a white LED are disclosed. The phosphor systems are excited by a non-visible to near-UV radiation source having an excitation wavelength ranging from about 250 to 420 nm. The phosphor system may comprise one phosphor, two phosphors, and may include optionally a third and even a fourth phosphor. In one embodiment of the present invention, the phosphor is a two phosphor system having a blue phosphor and a yellow phosphor, wherein the long wavelength end of the blue phosphor is substantially the same wavelength as the short wavelength end of the yellow phosphor. Alternatively, there may be a wavelength gap between the yellow and blue phosphors. The yellow phosphor may be phosphate or silicate-based, and the blue phosphor may be silicate or aluminate-based. Single phosphor systems excited by non-visible radiation are also disclosed. In other embodiments of present invention, a single phosphor is used to produce white light illumination, the single phosphor having a broad emission spectrum with a peak intensity ranging from about 520 to 560 nm.
1. A white LED comprising:
a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;
a yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 530 to 590 nm, wherein the yellow phosphor has the formula A 2 SiO 4 :Eu 2+ F and A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd, and wherein the fluorine dopant substitutes for oxygen; and
a blue phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 470 to 530 nm.
2. The white LED of claim 1 , wherein the radiation source comprises a light emitting diode (LED).
3. The white LED of claim 2 , wherein the radiation source comprises at least one semiconductor layer selected from the group consisting of GaN, ZnSe, and SiC, and at least one active region comprising a p-n junction selected from the group consisting of GaN, AlGaN, InGaN, and InAlGaN.
4. The white LED of claim 1 , wherein the yellow phosphor has the formula Sr 1-x-y Ba x Ca y SiO 4 :Eu +2 F; and where
0≦x≦0.8; and
0≦y≦0.8.
5. The white LED of claim 1 , wherein the yellow phosphor has the formula Sr 1-x-y Ba x Ca y SiO 4 :Eu 2+ F; and where
0≦x≦0.5; and
0≦y≦0.3.
6. The white LED of claim 1 , wherein the yellow phosphor has the formula Sr 1-x-y Ba x Ca y SiO 4 : Eu 2+ F; and where
0.5≦x≦0.7; and
0.2≦y≦0.5.
7. A white LED comprising:
a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;
a yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 530 to 590 nm; and
a blue phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 470 to 530 nm;
wherein the yellow phosphor has the formula (Sr 1-x-y Eu x Mn y ) 2 P 2+z O 7 ; and where
0.03≦x≦0.08;
0.06≦y≦0.16; and
0<z≦0.05.
8. The white LED of claim 1 , wherein the blue phosphor is selected from the group consisting of silicate-based phosphors and aluminate-based phosphors.
9. The white LED of claim 8 , wherein the blue phosphor has the formula Sr 1-x-y Mg x Ba y SiO 4 :Eu 2+ F; and where
0.5≦x≦1.0; and
0≦y≦1.0.
10. The white LED of claim 8 , wherein the blue phosphor has the formula Sr 1-x MgEu x Al 10 O 17 ; and where
0.2<x≦1.0.
11. The white LED of claim 8 , wherein the blue phosphor has the formula Sr x Al 14 O 25 :Eu +2 , where
x<4;
and where the amount of the Eu is limited to 10 mole percent.
12. A white LED comprising:
a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;
a yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with a peak intensity in a wavelength ranging from about 550 to 590 nm; wherein the yellow phosphor has the formula A 2 SiO 4 :Eu 2+ F and A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd, and wherein the fluorine dopant substitutes for oxygen and
a blue phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with a peak intensity in a wavelength ranging from about 480 to 510 nm.
13. The white LED of claim 12 , wherein the radiation source comprises a light emitting diode (LED).
14. The white LED of claim 13 , wherein the radiation source comprises at least one semiconductor layer selected from the group consisting of GaN, ZnSe, and SiC, and at least one active region comprising a p-n junction selected from the group consisting of GaN, AlGaN, InGaN, and InAlGaN.
15. The white LED of claim 12 , wherein the yellow phosphor has the formula
Sr 1-x-y Ba x Ca y SiO 4 :Eu +2 F; and where
0≦x≦0.08; and
0≦y≦0.8.
16. The white LED of claim 12 , wherein the yellow phosphor has the formula
Sr 1-x-y Ba x Ca y SiO 4 :Eu 2+ F; and where
0≦x≦0.5; and
0≦y≦0.3.
17. The white LED of claim 12 , wherein the yellow phosphor has the formula
Sr 1-x-y Ba x Ca y SiO 4 : Eu 2+ F; and where
0.5≦x≦0.7; and
0.2≦y≦0.5.
18. A white LED comprising:
a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;
a yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 530 to 590 nm; and
a blue phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 470 to 530 nm;
wherein the yellow phosphor has the formula (S 1-x-y Eu x Mn y ) 2 P 2+z O 7 ; and where
0.03≦x≦0.08;
0.06≦y≦0.16; and
0<z≦0.05.
19. The white LED of claim 12 , wherein the blue phosphor is selected from the group consisting of silicate-based phosphors and aluminate-based phosphors.
20. The white LED claim 19 , wherein the blue phosphor has the formula Sr 1-x-y Mg x Ba y SiO 4 :Eu 2+ F; and where
0.5≦x≦1.0; and
0≦y≦1.0.
21. The white LED of claim 19 , wherein the blue phosphor has the formula Sr 1-x MgEu x Al 10 O 17 ; and where
0.2<x≦1.0.
22. The white LED of claim 19 , wherein the blue phosphor has the formula Sr x Al 14 O 25 :Eu +2 , where
x≦4;
and where the amount of the Eu is limited to 10 mole percent.
23. A white LED having a single phosphor system, the phosphor system comprising:
a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm; and
a phosphor configured to absorb at least a portion of the radiation from the radiation source and emit a broad spectrum light with a peak intensity in a wavelength ranging from about 520 to 560 nm, wherein the yellow phosphor has the formula A 2 SiO 4 :Eu 2+ F and A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd, and wherein the fluorine dopant substitutes for oxygen.
24. The white LED of claim 23 , wherein the radiation source comprises a light emitting diode (LED).
25. The white LED of claim 24 , wherein the radiation source comprises at least one semiconductor layer selected from the group consisting of GaN, ZnSe, and SiC, and at least one active region comprising a p-n junction selected from the group consisting of GaN, AlGaN, InGaN, and InAlGaN.
26. The white LED of claim 23 , wherein the single phosphor has the formula
Sr 1-x-y Ba x Ca y SiO 4 :Eu +2 F; and where
0.3≦x≦0.8; and
0.1≦y≦0.5.
27. A method of producing white light illumination from a two-phosphor system, the method comprising:
providing a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;
exposing a yellow phosphor to at least a portion of the radiation from the radiation source to produce light having a wavelength ranging from about 530 to 590 nm;
exposing a blue phosphor to at least a portion of the radiation from the radiation source to produce light having a wavelength ranging from about 470 to 530 nm; and
mixing the light from the yellow phosphor with the light from the blue phosphor to produce the white illumination.