Wall plug or Radiant Effiency of LED's

lazerlover · May 12, 2009

Does anyone have a figure for this, for normal high powered white led's like cree or luxeon? I am not looking for luminous efficiency.

jtr1962 · May 12, 2009

For the best production white LEDs such as the Cree R2, the figure is roughly 30%. The highest lab figures I'm aware of so far would be around 50% for whites and 60% for blues.

zzonbi · May 12, 2009

there are royal blue leds available in a 425-500mW bin (+-7% @350mA 25C). So 38% efficient if Vf=3.2V, and in practice, with higher t, adding power supply losses, even less.

I guess these are also used with phosphors for the white leds. How efficient are the cool, neutral and warm white phosphors after all?

jtr1962 · May 14, 2009

zzonbi said:
How efficient are the cool, neutral and warm white phosphors after all?

The phosphors are actually not far off 100% theoretical efficency. Remember that for phosphor conversion there are inherent Stokes losses (i.e. Stokes shift ) which are larger the further apart the absorbed and reemitted wavelengths are (this is why phosphors which produce more red are less efficient). For white LEDs made with blue emitters and YAG phosphors the maximum theoretical phosphor conversion efficiency is around 82%. Actual phosphor conversion efficiency is somewhere in the high 70s.

zzonbi · May 18, 2009

So basically absorption-emission is done per photon and the efficiency is roughly the ratio of the peak wavelengths, the rest of energy going to heat.
Since blue and red are currently significantly more efficient among leds, green is better left to the phosphors, with the benefit of a more natural (continuous) emission spectrum for high CRI.
It seems what white leds use is a Cerium doped YAG.

Thanks for the educated answer.

Wall plug or Radiant Effiency of LED's

lazerlover

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jtr1962

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zzonbi

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