White LED tint and photons released

[FlashlightOCD]

I read that white LED's are made by applying phosphor coatings to natural colored LED's.

What is the natural color of the LEDS used in the L4/KL4?

Would it make sense that a tint colour closer to the natural LED color would be brighter than a tint further away from the natural LED colour?

Somebody in the B/S/T forum selling some L4's said that the one with the yellow tint was brighter than the one that was closer to white. I want to know if there is some physics involved that would explain this [or perhaps it was just the luck of the lotto].

I'm not sure I made the question clear, but please feel free to try your best to interpret and answer.

 

[RonM]

Good question. I've always wondered what the underlying color of a white LED was. My guess is it's some sort of blue. I don't remember white LEDs existing until before blue LEDs were invented, but I didn't really follow LEDs back then.

 

[milkyspit]

I, too, believe I had read that for Nichia LEDs at least, the natural color for the "white" LEDs is blue, which would explain why those LEDs tend to have a slight blue tint mixed into the white light.

What about Luxeons, though? Is their underlying color green, given the fact that many of the "white" ones tend toward green? Or possibly yellow?

Inquiring minds want to know. /ubbthreads/images/graemlins/smile.gif

 

[The_LED_Museum]

All white LEDs you can get (SMD, 3mm, 5mm, 1W LS, 5W LS) use a 460nm blue chip covered with a yellow-emitting phosphor. That's why most of them have a bluish tint, especially towards the center of the beam.

I'm not 100% sure what causes that "rotten dog urine green" color seen most often in 1W LS LEDs, but it's probably because too much phosphor got used. And I don't know at all why some LS LEDs have a purplish tint to them, instead of bluish.

 

[Wim Hertog]

The 'natural' color is 470nm blue and the same wavelenght is used to excite the phosphor in both normal 5mm LEDs and luxeons. The green tint is caused by the phosphor: too much phosphor = greenish, not enough = blue-purplish /ubbthreads/images/graemlins/smile.gif

 

[Wim Hertog]

Looks like we said the same thing on the same moment, Craig! /ubbthreads/images/graemlins/wink.gif

About the purplish tint...it doesn't seem logical to me either, I also thought not enough phosphor would cause a blue tint...

 

[FlashlightOCD]

[ QUOTE ]
Wim Hertog said:
Looks like we said the same thing on the same moment, Craig! /ubbthreads/images/graemlins/wink.gif


[/ QUOTE ]

Well there was a small 10 nm difference in what you said. /ubbthreads/images/graemlins/smile.gif

The second part of my crystal clear question was: Would less phosphor [towards the blue tint] allow more photons to be released, thus be slightly brighter than the same LED with more phosphor [yellow tint]?

 

[Wim Hertog]

</font><blockquote><font class="small">Als antwoord op:</font><hr />
FlashlightOCD said:
</font><blockquote><font class="small">Als antwoord op:</font><hr />
Wim Hertog said:
Looks like we said the same thing on the same moment, Craig! /ubbthreads/images/graemlins/wink.gif


[/ QUOTE ]

Well there was a small 10 nm difference in what you said. /ubbthreads/images/graemlins/smile.gif



[/ QUOTE ]


Your second part of the question: I think if you take 2 exactly the same blue emitters, yes. But in real world situations (wavelenght differences from the blue dice etc.)I don't think this is a general rule. I have an Arc AAA with a nice warm white beam and it is brighter than another Nichia LED (very blueish), both driven at +- 45 mA.