Koito's new red phosphor

Alaric Darconville

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Koito (the famed Tier 1 supplier to such as Toyota) is at it again, with a new red phosphor high-CRI white LEDs. It's called "Fluorine Oxygen Ligand Phosphor", or "FOLP:Eu2+​".

http://techon.nikkeibp.co.jp/atclen/news_en/15mk/011101836/ shows the sciency bit, but in short most white LEDs are somewhat deficient in red output, which makes higher CRIs difficult to attain.

This could mean that one day we have warm-to-neutral (or even strictly neutral) LED headlamps with high luminous efficacy and high CRI. Perhaps this could mean that existing 6000+ CCT LED headlamps will look antiquated and be undesirable, and soon we won't have to deal with all that "just like daylight" handwaving that is the current marketing spiel.
 

-Virgil-

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Not only for automotive, but also for home and commercial lighting, that is a very promising development! So is Seoul Semiconductor's purple-based (rather than blue-based) SunLike LED technology.

Now all we have to do is wait for these to make their way into LEDs appropriate for building headlamps around. I hope it happens. A lot of the objections to high color temperature (your 5500K, 6000K, 6500K types of ranges) will probably fall away once that giant blue peak in the spectrum gets chopped off.
 

Alaric Darconville

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I only hope the marketers latch on to this in such a way as they can paint the high-CCT LED sources as being just so much antiquated rubbish, and for REAL luxury/sport/race cars you gotta have this new technology that cuts "harmful blue light" or whatever...
 

PhotonWrangler

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Interesting. Thanks for the link! I'm looking forward to seeing commercial lamps based on this phosphor blend.

It looks like the excitation wavelength is centered around the 400nm violet wavelength. I recall that GE was experimenting with violet excitation and different phosphor blends under their VioLed banner. I don't know whether they've tried this specific phosphor, but they did manage to commercialize it, although I don't think it really got much traction in the market.
 
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Alaric Darconville

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It just occurred to me that one killer app would be a white 921 which would be great for a reversing lamp, or would work very well behind the red lens of a CHMSL.

It may be some time before they license this formula, though.
 

-Virgil-

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No exotic new phosphors or new technologies are needed to make white LEDs that work behind red lenses. Those already exist.
 

Magio

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Whats the point in that in way? Why don't you just use a red LED?
 

Magio

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We chose white diodes over colored diodes for their superior thermal management –– they don't lose intensity

Ehh...maybe they got some special LED but I have not seen a white LED that didn't loose intensity, just like a colored led. Maybe the percentage decrease is less or something like that but it does still loose intensity.
 

-Virgil-

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Ehh...maybe they got some special LED but I have not seen a white LED that didn't loose intensity, just like a colored led. Maybe the percentage decrease is less or something like that but it does still loose intensity.

Or maybe the R&D department at Peterson has "seen" (rigorously tested) more LEDs than you, and they specified ones that don't lose intensity at the drive currents used and with the heat sinking provided.
 

Magio

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I was always under the impression that the brightness of an LED was directly or indirectly related to its temperature and any change in temperature, however small it may be, meant a change in brightness however small it may be. Are you saying that is not true?
 

-Virgil-

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I was always under the impression that the brightness of an LED was directly or indirectly related to its temperature and any change in temperature, however small it may be, meant a change in brightness however small it may be. Are you saying that is not true?

No, I'm pretty sure I haven't said that. But you could double-check this thread; if you see me saying that, go ahead and point it out. :)
 

PhotonWrangler

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Brightness is affected by the amount of current flow, however like any semiconductor, there is a saturation point where any further increase in current won't produce more brightness, only damaging heat.
 

Magio

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Brightness is affected by the amount of current flow, however like any semiconductor, there is a saturation point where any further increase in current won't produce more brightness, only damaging heat.

Exactly. But it's my understanding that at any level of current flow, no matter how small, there will be a certain amount of heat generation. This heat generation leads to the led becoming slightly less efficient at producing light than it was when it's tempature was lower so the lumens drop until the temperature settles at a given level. If that is true I don't see how Peterson can claim that their LEDs don't loose any intensity. Virgil's post is so confusing and seemingly sarcastic with the smilie face I don't know what he's saying.
 

-Virgil-

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it's my understanding that at any level of current flow, no matter how small, there will be a certain amount of heat generation.

True.

This heat generation leads to the led becoming slightly less efficient

Above a certain point, yes, but you're ignoring or leaving out thermal management, that is the degree to which the LED is able to shed heat because it has been provided with adequate heat sinking in the design and construction of the lamp assembly, thus keeping the junction temperature below the temperature where output begins to droop.

I don't see how Peterson can claim that their LEDs don't loose any intensity.

Simple: they didn't ignore or leave out thermal management.

Virgil's post is so confusing and seemingly sarcastic with the smilie face I don't know what he's saying.

Among other things: THE WORD YOU'RE TRYING TO USE IS SPELLED L-O-S-E, WITH ONLY ONE "O". I typed that in uppercase letters so it would be nice and clear for you. :)
 
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Alaric Darconville

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Originally posted by Magio
This heat generation leads to the led becoming slightly less efficient at producing light than it was when it's (sic) tempature (sic) was lower so the lumens drop until the temperature settles at a given level. If that is true I don't see how Peterson can claim that their LEDs don't loose (sic) any intensity. Virgil's post is so confusing and seemingly sarcastic with the smilie face I don't know what he's saying.

What does "so the lumens drop until the temperature settles at a given level" even mean?

Peterson claims that the LEDs don't lose intensity based on their knowledge of the chemistry of the LEDs they've specified (see here*​), the type of thermal management they've employed, as well as through rigorous testing. This is Peterson, not PIAA.

*​The chart shows that blue and white LEDs (white ones being essentially a blue LED with an added phosphor) have a less-steep intensity drop-off from increased temperatures than red ones.
 
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ssanasisredna

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It's interesting, but not earth shattering. There is far more interest in narrow band quantum phosphors for high efficiency than High CRI since we can already do pretty well in that area . Realistically, beyond 2700/3000K, and "sunlight" no one has ever seen a so-called 100cri source.

GE, Soraa, Nichia, all have violet pumped LEDs with higher CRI, but always lower efficiency. That is no different from the vast majority of installed fluorescent which is mainly 80CRI since high CRI take an efficiency loss, just like LEDs from Stokes losses and no QE>1 phosphors seem to be on the horizon.

I really don't see any benefit to vehicle headlights. Any CRI > 80 is pretty much meaningless.
 
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