Are certain colors of LEDs more efficient?
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jtr1962
Flashaholic
It's hard to generalize here since there is so much variation among manufacturers so I'll try to stick mainly to the best examples regardless of manufacturer.
In terms of lumens per watt, the best I've heard so far is an estimated 65 to 70 lm/W from LEDs based on Cree's new 525 nm die (true green). However, the best whites aren't far behind at 55 to 60 lm/W (several manufacturers). The best red-orange is around 53 lm/W, amber about 40, and red about 40 (all from Lumileds). Cree's latest XT-27 blue die should give blue LEDs in the mid 20s.
However, if you're looking at strictly efficiency, meaning percentage of input power which is emitted as light, then I'd say Cree's XT-27 comes in on top at about 42%. If I recall there are also some red LEDs which have similar efficiency numbers but not spectacular lm/W numbers because the eye is less sensitive to red (and blue) light than to orange, amber, and especially green. The green Cree die I mentioned earlier is actually only 14% efficient despite the high lm/W number because the eye is very sensitive to light at that frequency.
As for numbers in the laboratory, we've exceeded 100 lm/W for red-orange and Cree recently announced 100 lm/W 5mm whites.
I hope others can continue where I've left off. This page should be of further help.
In terms of lumens per watt, the best I've heard so far is an estimated 65 to 70 lm/W from LEDs based on Cree's new 525 nm die (true green). However, the best whites aren't far behind at 55 to 60 lm/W (several manufacturers). The best red-orange is around 53 lm/W, amber about 40, and red about 40 (all from Lumileds). Cree's latest XT-27 blue die should give blue LEDs in the mid 20s.
However, if you're looking at strictly efficiency, meaning percentage of input power which is emitted as light, then I'd say Cree's XT-27 comes in on top at about 42%. If I recall there are also some red LEDs which have similar efficiency numbers but not spectacular lm/W numbers because the eye is less sensitive to red (and blue) light than to orange, amber, and especially green. The green Cree die I mentioned earlier is actually only 14% efficient despite the high lm/W number because the eye is very sensitive to light at that frequency.
As for numbers in the laboratory, we've exceeded 100 lm/W for red-orange and Cree recently announced 100 lm/W 5mm whites.
I hope others can continue where I've left off. This page should be of further help.
NewBie
*Retired*
This is dated, compared to the latest recent announcements, but it should get the point across:
DOE, Lawrence Berkeley National Labs and CREE
By combining the high performance chip designs with commercial phosphors in developmental LED packages, CREE was able to demonstrate white LEDs with record efficacies as high as 74 lumens per watt for a 0.3 x 0.3 mm2 chip operating at 20 mA, and 57 lumens per watt for a 0.9 x 0.9 mm2 chip operating at 350 mA.
...
Using high performance materials and bonding techniques to insure low thermal resistances in the critical heat flow path, a compact 1000 lumens LED lamp capable of dissipating 20 watts of heat was successfully demonstrated.
http://www.netl.doe.gov/ssl/highlights_cree.html
DOE, Lawrence Berkeley National Labs and CREE
By combining the high performance chip designs with commercial phosphors in developmental LED packages, CREE was able to demonstrate white LEDs with record efficacies as high as 74 lumens per watt for a 0.3 x 0.3 mm2 chip operating at 20 mA, and 57 lumens per watt for a 0.9 x 0.9 mm2 chip operating at 350 mA.
...
Using high performance materials and bonding techniques to insure low thermal resistances in the critical heat flow path, a compact 1000 lumens LED lamp capable of dissipating 20 watts of heat was successfully demonstrated.
http://www.netl.doe.gov/ssl/highlights_cree.html
jtr1962
Flashaholic
[ QUOTE ]
evan9162 said:
Wow. I didn't realize there was a huge gap in the spectrum, between 530 and 580nm.
[/ QUOTE ]
Actually, interestingly there are plenty of LEDs made in that gap, mostly around 565 nm, or "old school yellow green". For whatever reason the efficiency of them hasn't kept up with the other colors, perhaps because of lack of R&D due to relative lack of demand once "true green" came out. This is all the more amazing because you could have an LED in this range with a relatively small wallplug efficiency and still very high lm/W numbers due to the eye's sensitivity to light in this color range. For example, a mere 10% efficient at 555 nm would almost 70 lm/W. If we matched the efficiency of the best blue dies we would have close to 300 lm/W. However, development of yellow-green LEDs has been relative stagnant, and thus their efficiency is probably at best 10 lm/W or less.
evan9162 said:
Wow. I didn't realize there was a huge gap in the spectrum, between 530 and 580nm.
[/ QUOTE ]
Actually, interestingly there are plenty of LEDs made in that gap, mostly around 565 nm, or "old school yellow green". For whatever reason the efficiency of them hasn't kept up with the other colors, perhaps because of lack of R&D due to relative lack of demand once "true green" came out. This is all the more amazing because you could have an LED in this range with a relatively small wallplug efficiency and still very high lm/W numbers due to the eye's sensitivity to light in this color range. For example, a mere 10% efficient at 555 nm would almost 70 lm/W. If we matched the efficiency of the best blue dies we would have close to 300 lm/W. However, development of yellow-green LEDs has been relative stagnant, and thus their efficiency is probably at best 10 lm/W or less.
Canuke
Enlightened
[ QUOTE ]
jtr1962 said:
However, development of yellow-green LEDs has been relative stagnant, and thus their efficiency is probably at best 10 lm/W or less.
[/ QUOTE ]
In addition to the advent of true green, I suspect that another reason would be that of all the single-wavelength colors, yellow-green is the least appealling esthetically. It is to me.
jtr1962 said:
However, development of yellow-green LEDs has been relative stagnant, and thus their efficiency is probably at best 10 lm/W or less.
[/ QUOTE ]
In addition to the advent of true green, I suspect that another reason would be that of all the single-wavelength colors, yellow-green is the least appealling esthetically. It is to me.
VidPro
Flashlight Enthusiast
when it comes to MY human eye, the cyan, or red orange leds of even the small variety look very bright for the ammount of power.
the cyan (or turquoise) looks bright when aimed AT somthing.
so if i was to be stuck with a color, and not white, i would want to be stuck with cyan (green blue) for the best efficiency.
(has nothing to do with TYPE or Brand, just my eye)
the cyan (or turquoise) looks bright when aimed AT somthing.
so if i was to be stuck with a color, and not white, i would want to be stuck with cyan (green blue) for the best efficiency.
(has nothing to do with TYPE or Brand, just my eye)
