# white LED: 300 lumens/watt



## TMorita (Mar 5, 2008)

I haven't seen it mentioned here before, so I think it's new.

Article on it here:

http://www.ecogeek.org/content/view/1415/

Toshi


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## evan9162 (Mar 5, 2008)

I don't see how this is possible. They're covering commercially available blue LEDs with special crystals. Those LEDs don't have the efficiencies to support 300lm/W of white light, regardless of the conversion technology.

I think someone got their wires crossed here. They MIGHT be getting 300lm/W of green light using this method (blue LED with special crystals downconverting to green). But blue LED conversion efficiency isn't even at 50% yet AFAIK. 300lm/W is way more than 50% for white light.


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## Calina (Mar 5, 2008)

It was discussed before : https://www.candlepowerforums.com/threads/188268&highlight=luminous+efficiency

The article in New Scientist is referring to light conversion of 300 lm per watt of light not per watt of electrical input : 

"The final LEDs were also better than commercially available LEDs at creating visible light, giving off more than 300 lumens of visible light for every watt of all light emitted. This figure, known as the "luminous efficacy", is high compared to typical white LEDs."


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## 2xTrinity (Mar 5, 2008)

300 lumens per watt of _radiated light_ is not significantly different from ANY white LED on the market. 


If I wanted to make something sound super impressive, I could declare that the yellow-green indicator light on my wireless router is *680 lm/W* ... for every watt emitted!!! Too bad that figure is utterly irrelevant and potentially very confusing, as Y/G LEDs are among the least efficient in terms of lm/W input, despite emitting the most optimal wavelength.


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## evan9162 (Mar 5, 2008)

Calina said:


> It was discussed before : https://www.candlepowerforums.com/threads/188268&highlight=luminous+efficiency
> 
> The article in New Scientist is referring to light conversion of 300 lm per watt of light not per watt of electrical input :
> 
> "The final LEDs were also better than commercially available LEDs at creating visible light, giving off more than 300 lumens of visible light for every watt of all light emitted. This figure, known as the "luminous efficacy", is high compared to typical white LEDs."




The article later says typical white LEDs are 30 to 60 lm per watt of all light emitted. So it sounds like someone's got their terminology all screwed up. Current LEDs are 60 to 100 lm/W of electrical power, and their emission spectra is in the 260ish lm/W range. 

Not surprising that either the reporting, or the person talking to the reporter got things confused. Seems to happen more often than not.


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## LEDninja (Mar 5, 2008)

Note this LED produces Red Green Blue light only. Great for backlighting RGB LCD screens but in a flashlight yellow, orange cyan will show up as black.

The phosphor in current white LEDs have fairly wide spectrum. While blue, green, yellow are dominant, there is still some cyan, orange and red.


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## 2xTrinity (Mar 5, 2008)

LEDninja said:


> Note this LED produces Red Green Blue light only. Great for backlighting RGB LCD screens but in a flashlight yellow, orange cyan will show up as black.


Not exactly. Try taking actual red, green, and blue LEDs and shining them on things. Most things that appear yellow for example do so by absorbing blue light. They would therefore reflect both red and green light together and the combination will still appear yellow, only with a slightly different tint or cast to it than under a broad-spectrum light. There are very few things that reflect only a narrow band of wavelengths like spectral cyan or spectral yellow, so as to appear BLACK under RGB.

As far as backlighting RGB LCD screens, the best way to do that would be to backlight the entire screen with blue lght, then put the red and green phosphors on the red/green pixel regions, with no phoshphor on the blue regions. Right there you eliminate the majority of the filtering losses.


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## LEDninja (Mar 5, 2008)

2xTrinity said:


> As far as backlighting RGB LCD screens, the best way to do that would be to backlight the entire screen with blue lght, then put the red and green phosphors on the red/green pixel regions, with no phoshphor on the blue regions. Right there you eliminate the majority of the filtering losses.


Maybe put those tuned nano crystals on the red/green pixels instead of on the LED. It should be more efficient than phosphors.


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## DM51 (Mar 5, 2008)

There is an existing thread here, where this discussion can be continued.


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## 2xTrinity (Mar 5, 2008)

LEDninja said:


> Maybe put those tuned nano crystals on the red/green pixels instead of on the LED. It should be more efficient than phosphors.


Agreed. Also, having the nano crystals ON the pixels, with the LCD only controlling how much blue light is used to pump each crystal, would allow for wider viewing angle than traditional LCDs, more like a CRT, which has electron phosphor directly on the screen. The biggest drawback I can think of that is that with the nanocrystals on the screen, they might actually fluoresce/react to ambient lighting.


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