Phosphor-converted white light emitting diodes having narrow-band green phosphors
View Patent ↗In one aspect, a phosphor converted white light LED comprising a narrow green phosphor rather than a conventional broad green phosphor may simultaneously exhibit high R9, and high Luminance Efficacy of Radiation, optionally without use of a deep red phosphor to maintain desired red color rendering. In another aspect, a phosphor converted white light LED comprising a narrow green phosphor rather than a conventional broad green phosphor may provide an emission spectrum exhibiting a significant dip in the yellow region of the spectrum and thereby provide high red-green contrast without use of a filter. The yellow dip may be shallower than in conventional devices, and the device may therefore be brighter, while maintaining desired CRI and R9.
1. A light emitting device comprising:
a semiconductor light source emitting blue light;
a first phosphor arranged to be excited by the blue light emitted by the semiconductor light source and in response emit green light having a peak emission at from about 500 nm to about 550 nm with a full width at half maximum of about 30 nm to about 50 nm; and
a second phosphor arranged to be excited by the blue light emitted by the semiconductor light source and in response emit red light having a peak emission at a wavelength less than or equal to about 635 nm;
wherein an overall emission spectrum from the light emitting device has a depression between about 550 nm and about 580 nm, and the minimum intensity in the depression is greater than or equal to about 25% and less than or equal to about 75% of the maximum intensity in the overall emission spectrum in the range from about 400 nm to about 700 nm.
2. The light emitting device of claim 1 , wherein the blue light emitted by the semiconductor light source has a peak at from about 430 nm to about 465 nm and a full width at half maximum of about 10 nm to about 35 nm.
3. The light emitting device of claim 1 , wherein the green light emitted by the first phosphor has a full width at half maximum of less than or equal to about 45 nm.
4. The light emitting device of claim 1 , wherein the red light emitted by the second phosphor has a full width at half maximum of about 70 nm to about 100 nm.
5. The light emitting device of claim 1 , wherein the overall emission spectrum from the light emitting device has an R9 color rendering value of greater than or equal to about 40.
6. The light emitting device of claim 1 , wherein the overall emission spectrum from the light emitting device has a CRI greater than or equal to about 80.
7. The light emitting device of claim 1 , wherein the overall emission spectrum from the light emitting device has a luminous efficacy of radiation greater than or equal to about 280.
8. The light emitting device of claim 1 , wherein the overall emission spectrum from the light emitting device has an R9 color rendering value of greater than or equal to about 50 and a luminous efficacy of radiation greater than or equal to about 300.
9. The light emitting device of claim 1 , wherein the light emitting device does not comprise a phosphor emitting light having a peak emission greater than or equal to about 635 nm.
10. The light emitting device of claim 1 , wherein:
the first phosphor emits green light having a peak emission at from about 500 nm to about 540 nm; and
the overall emission spectrum from the light emitting device has an R9 color rendering value of greater than or equal to about 40.
11. The light emitting device of claim 10 , wherein the first phosphor emits green light having a peak emission at from about 520 nm to about 540 nm.
12. The light emitting device of claim 10 , wherein the blue light emitted by the semiconductor light source has a peak at from about 430 nm to about 465 nm and a full width at half maximum of about 10 nm to about 35 nm.
13. The light emitting device of claim 10 , wherein the green light emitted by the first phosphor has a full width at half maximum of less than or equal to about 45 nm.
14. The light emitting device of claim 10 , wherein the red light emitted by the second phosphor has a full width at half maximum of about 70 nm to about 100 nm.
15. The light emitting device of claim 10 , wherein the overall emission spectrum from the light emitting device has a CRI greater than or equal to about 80.
16. The light emitting device of claim 10 , wherein the overall emission spectrum from the light emitting device has a luminous efficacy of radiation greater than or equal to about 280.
17. The light emitting device of claim 10 , wherein the overall emission spectrum from the light emitting device has an R9 color rendering value of greater than or equal to about 50 and a luminous efficacy of radiation greater than or equal to about 300.
18. The light emitting device of claim 10 , wherein the light emitting device does not comprise a phosphor emitting light having a peak emission greater than or equal to about 635 nm.
19. The light emitting device of claim 1 , wherein
the first phosphor emits green light having a peak emission at from about 500 nm to about 540 nm;
the second phosphor emits green light having a peak emission at less than or equal to about 620 nm; and
the overall emission spectrum from the light emitting device has an R9 color rendering value of greater than or equal to about 0.
20. The light emitting device of claim 19 , wherein the blue light emitted by the semiconductor light source has a peak at from about 430 nm to about 465 nm and a full width at half maximum of about 10 nm to about 35 nm.
21. The light emitting device of claim 19 , wherein the green light emitted by the first phosphor has a full width at half maximum of less than or equal to about 45 nm.
22. The light emitting device of claim 19 , wherein the red light emitted by the second phosphor has a full width at half maximum of about 70 nm to about 100 nm.
23. The light emitting device of claim 19 , wherein the overall emission spectrum from the light emitting device has a CRI greater than or equal to about 80.
24. The light emitting device of claim 19 , wherein the overall emission spectrum from the light emitting device has a luminous efficacy of radiation greater than or equal to about 280.
25. The light emitting device of claim 19 , wherein the overall emission spectrum from the light emitting device has an R9 color rendering value of greater than or equal to about 50 and a luminous efficacy of radiation greater than or equal to about 300.
26. The light emitting device of claim 19 , wherein the light emitting device does not comprise a phosphor emitting light having a peak emission greater than or equal to about 635 nm.
27. The light emitting device of claim 1 , wherein the first phosphor does not comprise quantum dots.
28. The light emitting device of claim 1 , wherein the first phosphor comprises quantum dots.
29. The light emitting device of claim 1 , wherein the first phosphor is disposed directly on the semiconductor light source.
30. The light emitting device of any of claim 1 , wherein the light emitting device does not comprise a filter producing a depression between about 550 nm and about 590 nm.