# The first LEDs to utilize quantum dots



## saabluster (May 11, 2008)

There has been many posts about the great Q dot hope for LEDs and it now seems to have arrived. A lot sooner than most expected looking back at some of the old posts. Granted it is in a low power device but how great it is to see it on the market at all this soon. Lumileds and Cree need to put this technology in there products ASAP.


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## IMSabbel (May 11, 2008)

Thats nice.
While they are not "up there" yet for flashlight purposes, they are still nice to play around with.

Especially considering the way they work, which makes setups that much easier electrically (all colours have the same forward voltage, and should show the same thermal behaviour, for example).


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## SemiMan (May 11, 2008)

They all have the same forward voltage because they all use the same "pump" LED, i.e. electrically they are all exactly the same LED.

This is just a phosphor technology and too that end not a "quantum" leap in performance for flashlights. For our needs, what we are looking for it bright and consistent. Phosphors themselves are already consistent, what is missing is the matching between the phosphor and the LED which there are existing technologies already coming on the market to address. Current phosphors are relatively efficient as well.

Semiman


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## snarfer (May 11, 2008)

They may not be all that interesting for flashlight applications, but for other applications, such as fixed lighting, they are very important. It looks like they are offering high efficiency phosphors in colors that were not previously available. Also they are offering the phosphors themselves without the LEDs, and I haven't seen that before. It offers up a lot of possibilities in terms of lighting design.


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## IMSabbel (May 12, 2008)

Well, there are also ways of using quantum dots for leds that arent straight phosphor replacements.

You can also get direct recombination inside the quantum dots, where you can hand-tune the confined bandgaps. I dont know what this LED uses, but seeing that quantum dot lasers have worked for a while...

(Real Quantum-Dot leds would be neat because you can get higher light extraction efficiency practiacally for free)


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## Viper715 (Dec 7, 2009)

Sorry for bumping an old post here but Gizmodo just had a article on Quantum Dots.

http://gizmodo.com/5421083/how-quantum-dots-could-make-leds-as-warm-as-candlelight


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## spencer (Dec 7, 2009)

If quantum dots take light and re-emit it at a different wavelength, won't that lower CRI? Or is my REALLY basic understanding not enough?


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## Th232 (Dec 7, 2009)

It can increase or lower the CRI, depending on what the original wavelength distribution is and how it'll be redistributed.


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## jtr1962 (Dec 8, 2009)

It seems they're mostly using them to convert some blue to red. This is fine up to a point. I've mentioned many times that most white LEDs are deficient in red. But they grossly overdid in that picture. My first thought seeing that lamp was "Where's the great pumpkin, Charlie Brown".


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## PhantomPhoton (Dec 8, 2009)

saabluster said:


> There has been many posts about the great Q dot hope for LEDs and it now seems to have arrived. A lot sooner than most expected looking back at some of the old posts. Granted it is in a low power device but how great it is to see it on the market at all this soon. Lumileds and Cree need to put this technology in there products ASAP.



The thing is it's been over a year since the OP and the linked website still looks like vaporware... unless I've completely missed the boat on these somewhere. :candle:


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## saabluster (Dec 8, 2009)

PhantomPhoton said:


> The thing is it's been over a year since the OP and the linked website still looks like vaporware... unless I've completely missed the boat on these somewhere. :candle:


Yeah you missed the boat. I've had some of these to play with for some time now.


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## JohnR66 (Dec 8, 2009)

So what happened to Evident Tech and the Evidot LEDs? For some time now I can't access the LED products anymore.

They were expensive in small numbers. Better to buy a Dotstrand xmas lights and hack out the LEDs.

Here is a video of adding quantum dots to a blue LED.
http://www.youtube.com/watch?v=SVyC8JW-Q3A


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## EricB (Dec 8, 2009)

Wow, is that process reversible? (and able to be controlled back and forth in lighting applications)? That could be what I've been asking about for years.
He not only changed the blue to red, but to green, amber, orange, and purple as well.
I read about this before, but I don't remember it being that versatile, to change to all the colors. I remember now, on the site (in that table), it looks like they van only alter the different colors a bit (like making peach out of the orange LED). Or is is a one way conversion?

Here also, is where I had reported some new technology promising a "tunable" LED:
https://www.candlepowerforums.com/posts/3139389&postcount=16

Alsom, one of the sites says:

"Unlike filters, the method *does not soak up light and hurt efficiency* — they're taking "blue photons from the LED and outputting red photons from the quantum dots." "


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## Th232 (Dec 8, 2009)

saabluster said:


> Yeah you missed the boat. I've had some of these to play with for some time now.



How'd they turn out relative to the equivalent Nichias and Crees?


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## saabluster (Dec 8, 2009)

Th232 said:


> How'd they turn out relative to the equivalent Nichias and Crees?


Extremely dim. It would take quite a few of them to put out anything useful. I'm sure that has more to do with the base LEDs they used than the quantum dots themselves but there is no way to know for sure.


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## Th232 (Dec 8, 2009)

Thanks for the info, bit of a bummer there. Hopefully someone else will also pick up the technology.


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## txmatt (Dec 10, 2009)

Some new coverage of quantum dot usage in LED's from last week's Materials Research Society fall meeting in Boston...

http://spectrum.ieee.org/semiconductors/optoelectronics/quantum-dots-enhance-led-lighting


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## JohnR66 (Dec 10, 2009)

EricB said:


> Wow, is that process reversible? (and able to be controlled back and forth in lighting applications)? That could be what I've been asking about for years.
> He not only changed the blue to red, but to green, amber, orange, and purple as well.
> I read about this before, but I don't remember it being that versatile, to change to all the colors. I remember now, on the site (in that table), it looks like they van only alter the different colors a bit (like making peach out of the orange LED). Or is is a one way conversion?
> 
> ...



I was thinking of taking blue 5mm LEDs and filing down the LED so it is flat and close to the die. Mixing Qdots like paint and then mixing them with clear two part epoxy like the kind at the hardware store. You could make any color LED you want although it would be a wide angle emmitter.


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## chrisWELD (Mar 9, 2010)

Interesting and clear video on quantum dot use to modify LED lighting:

http://audiovideo.economist.com/?fr_story=07a1cab21d657cb00f9066aea334135bf69111a2&rf=bm


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## saabluster (Mar 9, 2010)

chrisWELD said:


> Interesting and clear video on quantum dot use to modify LED lighting:
> 
> http://audiovideo.economist.com/?fr_story=07a1cab21d657cb00f9066aea334135bf69111a2&rf=bm


Nothing new there but cool nonetheless. Thanks.


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## zzonbi (Mar 16, 2010)

Do they really have no conversion losses? Could they use also a longer wavelength for input?


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## R33E8 (Mar 16, 2010)

zzonbi said:


> Do they really have no conversion losses? Could they use also a longer wavelength for input?



No, they do have conversion losses.. And the wavelength needed is usually closer to 400nm.. When I was making quantum dots I managed to get the excitation peak up to around 420nm or so.. I didn't have enough time and ended up switching schools so I could not continue working on it..


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## zzonbi (Mar 17, 2010)

So they're more about the convenience of trimming the output spectrum, rather than losses, compared to phosphors. Or cheapness, judging by the amount required.


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## mejesster (Apr 2, 2010)

I've met the man from the Economist video. He's my girlfriend's cousin.

I'm really looking forward to LED lighting indoors with a nice color reproduction. Right now, I use the Z-Bar LED floor lamp, which I like a lot, but would be even nicer if the light weren't so cold.

Has anyone seen commercially available QD implementations yet, or just prototypes/samples/etc?


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## saabluster (Apr 2, 2010)

mejesster said:


> Has anyone seen commercially available QD implementations yet, or just prototypes/samples/etc?


Well it appears you can longer order the ones first linked to. Wonder what happened. Good thing I got some while I could.


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## saabluster (Apr 2, 2010)

saabluster said:


> Well it appears you can longer order the ones first linked to. Wonder what happened. Good thing I got some while I could.



Well I found out what happened. 

"In a statement, Ballinger said the company had to file for bankruptcy because of mounting costs necessary to defend itself in an ongoing patent infringement lawsuit in Texas."

Bummer


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