Quantum-dot LED screens may soon rival OLEDs and LCDs

Dec 13, 2010 by Lin Edwards report
Quantum Dot LEDs (QLEDs). Image: QD Vision

(PhysOrg.com) -- A partnership has been formed between US, South Korean and Belgian companies to develop quantum-dot light emitting diode (QLED) displays to rival the organic light emitting diode (OLED) markets and eventually also LCD applications such as computer screens and televisions.

Massachusetts company QD Vision, a spin-off from the Massachusetts Institute of Technology, has joined with LG , headquartered at Seoul, and Solvay, a chemical company based in Belgium, to develop and manufacture active matrix QLED displays.

The technology uses nano-scale semiconducting crystals that shine when exposed to electrical current () or light (such as that produced by LEDs), producing a bright light and pure colors. QD Vision is working on electroluminescence, which is the best option for creating a display in which are the main element.

Chief Technology Officer with QD Vision, Seth Coe-Sullivan, said the project is approaching the point at which it can be commercialized as a rival to the displays. Coe-Sullivan said the OLEDs have some unresolved challenges, especially for applications needing larger displays, and he sees QLEDs as the way to solve them.

OLEDs are created using a “shadow mask” that allows them to be patterned as they are deposited, but this technique is only accurate for small displays. Since QLEDs are manufactured without the need for a shadow mask, the problem of reduced accuracy does not arise. The quantum dots can be suspended in a liquid and deposited using a range of techniques, even including ink-jet printing, onto extremely thin, flexible, or transparent substrates.

Coe-Sullivan said another disadvantage of OLEDs is that some need color filters to enable them to produce pure colors, but QLEDs produce pure, rich colors from the start. He said QLEDs are "fundamentally superior" to OLEDs in the way they convert electrons to photons, and this means much greater energy efficiency. They are also cheaper to make.

One of the challenges for the QLED developers is that currently the best QLEDs have a lifetime of only 10,000 hours, which is not enough for a large display. Another is making sure the color reproduction is uniform throughout the spectrum. Coe-Sullivan said the company has made a great deal of progress and commercialization should soon be possible, but he declined to give a precise timeline.

QD Vision is not the only company developing electroluminescent quantum dot displays, as Nanosys, a company based in Silicon Valley, is working on a product that includes a strip of quantum dots on a liquid crystal display backlight to improve the energy efficiency and color quality.

Explore further: Japan firm showcases Bat-Signal of the future

More information: www.qdvision.com/qled-technology

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User comments : 28

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Raveon
not rated yet Dec 13, 2010
Maybe this is getting closer to the perfect display. Where every individual pixel is capable of every color instead of having 3 or 4 color elements to each pixel to generate all the colors. A single pixel that can change color would also automatically give about a 50 to 100% increase in resolution for the same size element.
El_Nose
not rated yet Dec 13, 2010
10000 hours is fine for me -- I don;t watch tv much and after 7 years my timer on my tv states its had about 4000 hrs of usage, and that sounds about right to me.

-- umm as it stand each pixel IS one color - a pixel is defined as an RGB group 0x123456 with number '12' - red '34'- green '56'-blue with a hexideciaml system to determine intensity of each color. So by definition we are already at your perfect display of the future -- manufacturers's determine pixel size per device because we have locked ourselves into HD formats those numebrs 1020 and 780 mean how many horizontal lines are on the screen. well if the screen gets bigger and the number of lines stay the same the pixel gets bigger - and its only then that you can tell by getting closer to it - that each pixel is made of a mixture of colors -- this however doesn't mean its ineffecient.
dtxx
3 / 5 (2) Dec 13, 2010
That's still about 90 minutes per day. Low for sure, but I'd guess I've probably watched 90 minutes of TV in the last year. I'm just much more interested at looking at other things on a screen. The pace of most TV shows seems to be suited to an audience with an IQ of about 80 and some serious working memory deficits.
lexington
not rated yet Dec 13, 2010
Most people are going to watch a few hours of TV every day. So these would currently die in half a year or less. However extending the life time doesn't seem like a fundamentally unsolvable issue so I'm looking forward to seeing this tech implemented.
Raveon
5 / 5 (1) Dec 13, 2010
.... umm as it stand each pixel IS one color - a pixel is defined as an RGB group....


Umm, you don't know what you are talking about and you contradict yourself in the same sentence. First you say it's one color and then you define it as a group of 3 colors. It GENERATES one color to the human eye at a distance but look close and you see 3 or 4 colors. We are talking a display pixel here not an image pixel.

RGB is red, green and blue, 3 colors. A pixel is a color group made of 3 separate elements, sometimes 4 (RGBY). If each of those 4 elements in a pixel could generate all colors instead of 1 color it would be 4 pixels instead of 1 and the display would have twice the resolution. It takes 4 times the pixels to double resolution. Actually you would have more because the elements aren't square and a pixel is.
Foundation
5 / 5 (1) Dec 13, 2010
Most people are going to watch a few hours of TV every day. So these would currently die in half a year or less.

55 hours or more TV a day (??) is called 'a few hours' nowadays?
This explains so much...
Bonkers
not rated yet Dec 13, 2010
Raveon
have a look at the CIE chromaticity chart, to generate an arbitrary colour you need to generate quantities of R,G, and B light - a single tuneable wavelength will not do - it will not get you off the periphery of the colour chart. Besides i think the colour of a Q-dot emitter is not electrically tuneable, its physically related to the dot size. The resolution enhancement you mention is already achieved with colour-sequential displays, like on the tektronix "lunchbox" 'scopes, and TI micromirror array devices, but they do generate artefacts if your eye swivels - the RGB breaks up.
lexington
not rated yet Dec 13, 2010
Most people are going to watch a few hours of TV every day. So these would currently die in half a year or less.

55 hours or more TV a day (??) is called 'a few hours' nowadays?
This explains so much...


Woah, miscalculation on my part I made days into hours! So we're looking at more like six years of working time. Bump that up to eight or ten years and it'll be ready to do. Sweet.
bluehigh
1 / 5 (2) Dec 13, 2010
Bonkers - a single tunable wavelength emitter could produce any colour you like. Nothing to do with RGB colour mixing.
Raveon
not rated yet Dec 14, 2010
Actually I was wrong in part. A single emitter can't produce some of the colors we perceive because the human eye has separate red, green and blue receptors.

Some combination of red, green and blue emitters is required to produce the full spectrum of colors we perceive in a pixel, which is different than the light spectrum. For instance magenta isn't in the light color spectrum but it is in our perceived color spectrum, it's a combination of frequencies. One display company has added a yellow emitter but that is probably due to phosphors not being able to produce pure red, green or blue.

To make a long story short, displays will always have pixels made of 3 bars - red, green and blue (because bars make a square pixel better than 3 dots can).
CreepyD
not rated yet Dec 14, 2010
It looks like LCD/LED/Plasma can all manage at least 50-100k hours.
10k hours at 10 hours a day (say someone not working and at home all day) would give you 173 days, which is pretty poor.
I would have thought they would want a heavy user to always make it past 1 year of usage.
Hope they get there as it sounds great.
mysticshakra
not rated yet Dec 14, 2010
So there is nothing quantum about quantum dots. Quantum seems to have become the latest buzz word carrying no substance to hit the marketplace.
Bonkers
not rated yet Dec 14, 2010
Raveon - well fessed, it makes commenting worthwhile if one knows that a greater understanding has been facilitated.
Bluehigh - your statement is simply incorrect, please refer to CIE chromaticity and colour theory.
Mysticshakra - (is that really your name? ) - Q-dots are genuinely quantum entities, much as we all dislike meaningless buzzwords, this isn't one of them...
HealingMindN
not rated yet Dec 14, 2010
Wouldn't it be cool if the QLED screens open up some kind of quantum universe that affects our minds, so it looks like we can reach into the screen and grab stuff? Then when we pull our hands out, they're backwards like from that outer limits ep.
KomMaelstrom
not rated yet Dec 15, 2010
I like how the United States' acronym reads out simply as just "us". So arrogant, Americans.
bluehigh
1 / 5 (2) Dec 15, 2010
Bonkers: every colour your eyes perceive is the result of an impacting light frequency with perhaps harmonics. Any colour you like can always be generated by a tunable light source. Its simple optics and has nothing to do with the approximations in chromaticity charts. Perhaps it is you in need of a broader understanding.
Raveon
not rated yet Dec 17, 2010
It looks like LCD/LED/Plasma can all manage at least 50-100k hours.
10k hours at 10 hours a day (say someone not working and at home all day) would give you 173 days, which is pretty poor.
I would have thought they would want a heavy user to always make it past 1 year of usage.
Hope they get there as it sounds great.


That's 1000 days not 173. But you are correct, 50k to 100k is generally the requirement for a decent lifespan, 10k isn't much. I have a feeling that many of the LCD's people have bought recently aren't going to make it to the 50k mark either though. I have a 25" Toshiba CRT and it must be close to the 100k mark and the picture is still perfect. It will probably still be working when the Samsung HD LCD I bought this year quits.
Raveon
not rated yet Dec 17, 2010
Bonkers: every colour your eyes perceive is the result of an impacting light frequency with perhaps harmonics. Any colour you like can always be generated by a tunable light source. Its simple optics and has nothing to do with the approximations in chromaticity charts. Perhaps it is you in need of a broader understanding.


Not true.
http://en.wikiped.../Magenta
http://www.null-h..._bizarre
Mira_Musiclab
not rated yet Dec 17, 2010
I know fairly little about the cost-complexity-toxicity involved in making QLED. But considering that they can be printed on such simple substrates, it's kind of exciting.
To have a point where you can 'rebuild' a monitor or tv, by replacing a film, rather than the waste of a big CRT. (driving circuitry aside, I suppose)
Would be nice to see if LCD and OLED's could take that same approach..
Raveon
5 / 5 (4) Dec 17, 2010
That will never happen, we move closer to a complete 'throw it away when it's broke' society every day instead. The free market dictates this, not common sense. EVERYTHING could and should be rebuildable or recyclable if we wanted but it will never happen until we start to drown in our waste like a culture in a petri dish and the earth is a petri dish, we are as stupid as a bacterium not to know it.

Human society is following the same path as a petri dish too, the culture dies from overpopulation by either consuming all the resources or dying from its waste. I am sure it also happens because most of the bacteria are republicans, believe in the one true ober-bacterium, his son is going to save them and all the other bacteria who are trying to tell them what is going to happen are just dumb disbelievers or scientists.
Mira_Musiclab
not rated yet Dec 17, 2010
@Raveon,

Yeah, I fear you may be correct. It doesn't fit into a capitalist model very well, what with devices lasting lifetimes vs breaking down in 5 years..

Oh well, hope for the best I suppose..
Palli
not rated yet Dec 18, 2010
Wouldn't it be cool if the QLED screens open up some kind of quantum universe that affects our minds, so it looks like we can reach into the screen and grab stuff? Then when we pull our hands out, they're backwards like from that outer limits ep.

Like when you play QBERT?
bluehigh
2.3 / 5 (3) Dec 18, 2010
@Raveon
"The color magenta stimulates both the "red cones" and the "blue cones" in your retina. A combination of red light and blue light will do
exactly the same thing. As a result, a combination of red and blue light produces the same effect as magenta light. We then say that red and blue produce magenta."

US Department of Energy
Physics Department

More authoritative than an unreferenced Wikipedia entry!

Try 7494813828000000 Hz for Magenta and your eyes will sense a red and blue value and then your brian will re-assemble the the sensory input back onto the originally transmitted colour of Magenta.

Bonkers
not rated yet Dec 20, 2010
OK , how do you get "white" with your tuneable colour source? - or in fact any colour that is off the perimeter of the colour triangle? - pink, for instance.
Your "Magenta" frequency above gets only one hit on Google, did you make it up? - try googling "magenta wavelength" for previous, informed discussion. I stick by my point that the colour triangle (CIE chromaticity) contains all the colours perceptible to the human eye, and the arc perimeter has the pure wavelengths defined in nm, the straight perimeter has magenta and other combinations of red and blue. These, and all the internal unsaturated colours require a mix of at least 2 pure colours.
My understanding is fine, it is correct and complete (in this matter) - so no need for it to be broadened, but thanks for the offer.
bluehigh
1 / 5 (2) Dec 20, 2010
If needed a tuneable light source can oscillate through the visble spectrum at a rate faster than the persistence time of the (human) eye and white would be observed. Likewise it could be turned off and go black. In fact if you insist in needing some superimposed harmonics to produce a color then a tunable light source can be modulated to create any perceptual effect you desire.

So back to the original proposition: A tunable light source can emit any colour you like. If you want, I can modulate it for your desired special
effects.
bluehigh
1 / 5 (2) Dec 20, 2010
Unfortunately, Bonkers, you are a victim of an urban myth that is in need of debunking. Even your chosen Pink of any hue, shade or tint is
transmissible by a tunable light source. White (and Black) of course are simply a red(!)herring in your argument. What you are misunderstanding is that the "color triangle" as you put it, is just a representation of what the (mostly human) eye can sense based on its structure. It is a sensory approximation of reality that the (human) brain discerns using its S,M and L receptors signal to perceive incoming data. Simply a a way to understand how the human eye can assign values. The idea that extra (or non) spectral colors exist is a misconception that has been common for too long. Unfortunately this kind of poor thinking is re-inforced by popularist Google results and consensus info stores like Wikipedia.
bluehigh
1 / 5 (2) Dec 20, 2010
Wow! A Google hit on a result from a subjective experiment I did using our equipment here only yesterday. Is that a confirmation? A Google
search, once you get past the incoherent babble of wave superposition and the latest twitter claims that Magenta is not a color, shows informed
discussion is based on the philosophical idea of Qualia. At this point its possible to start to argue the definition of the word color (colour) and (what might or might not be spectral/extra spectral or non spectral) and is pointless in the context of the physorg article as the discussion is reduced to semantics.

In the meanwhile QLEDS are only tunable through physical construction - so far.
rgwalther
not rated yet Feb 10, 2011
I like how the United States' acronym reads out simply as just "us". So arrogant, Americans.


I'd say that anyone wishing for a whirlpool to arrive is somewhat destructive and arrogant...