# Most efficient LED of any colour by radiant flux



## bbb74 (Mar 13, 2012)

I'm probably going to get my terminology wrong but I'll try not to.

I'm wondering which LED model, of any colour including white, red, blue, green etc is the most efficient at converting input power to light output (*radiant flux*). I'm not asking which has the highest luminous efficiency (lumens/watt) because that takes into account the eye's differing sensitivity to different frequencies of light.

Thanks!


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## slebans (Mar 13, 2012)

For the top Bins, 1 watt of input power, at 25C ambient, with Junction temps below 100C:

Cree XT-E Royal Blue - 50-52% WPE
Cree XM-L Cool White - 50% WPE
Osram HyperRed - 40-44% WPE

This is off the top of my head. You can search the Datasheets for actual values.

Stephen Lebans


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## MikeAusC (Mar 13, 2012)

No Cree datasheets make any reference to Radiant Flux for White LEDs - no-one uses those values for White LEDs.

Since White LEDs are just Blue LEDs with Phosphor in the optical path, the Radiant Flux for White will always be much less than for Blue.


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## RoGuE_StreaK (Mar 13, 2012)

Didn't a recent thread indicate that green was the most efficient at converting energy? May have been outdated data though.


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## bshanahan14rulz (Mar 13, 2012)

I think green would be least efficient. It is, however, more easily seen by the eye. i.e. same "amount" of green photons would look much brighter than the same number of red photons.


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## bbb74 (Mar 13, 2012)

MikeAusC said:


> No Cree datasheets make any reference to Radiant Flux for White LEDs - no-one uses those values for White LEDs.
> 
> Since White LEDs are just Blue LEDs with Phosphor in the optical path, the Radiant Flux for White will always be much less than for Blue.



That's what I was thinking, that the phosphor would result in lower radiant flux so one of the coloured type leds would probably "win" but I wasn't sure which colour is the most efficient.

Green wins on lumens/watt but that's only because the eye is most sensitive to green. So I was wondering if red or blue (or green really) were the most efficient at converting input power to radiant flux?


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