MIT Develops Quantum-Dot OLEDs

deglr6328 writes "Researchers at MIT have developed a new type of Organic Light emitting Diode (OLED) using Cadmium Selenium Quantum Dots as the electron-hole recombination layer. It is widely believed that the next generation of flexible flat panel display technologies will be self luminous (non-backlit) organic light emitting diodes. However, the efficiency and lifespan of both small molecule and polymer type OLEDs, to date, has been poor for small wavelength emitting compounds. Using quantum dots as the emissive layer in OLEDs potentially solves both of these problems since they are inorganic and won't degrade, and they have a theoretical maximum quantum efficiency of near 100%. Mmmmm ... can't wait to buy my first roll-up display!"

Comments

Cool... but when?

[httpamphibio.us]

Haven't roll-up displays been "two years away" for about seven years now?

I love the concept... but really, shouldn't we have at least one low quality, high priced, first generation consumer product by now?

roll up displays

[Gary Franczyk]

I hope they are as sharp and readable as the current LCD screens. One great advantage to LCD screens is that they are significantly easier on the eyes than CRT monitors.

If this new technology is cheaper or has some other substantial improvement over LCDs, most manufacturers may stop selling LCD monitors or laptops using LCD screens. Those of us that look for easy to read screens may lose out.

Like those screens in Total Recall

[forged]

Remember the movie Total Recall? At breakfast we saw Doug and his wife surrounded by these displays seamelessly integrated to the walls, such that they had either Lake View, Montains View, etc. Or just regular TV programs captioned in a corner of the screen.

Hopefully this is the kind of technology breakthrough that will make it possible to get these massive flat screens in our living rooms one day!

Keep waiting

[nesneros]

I remember being a freshman in college, and making a dork of myself by telling all my friends how these things would be out in a year and how massively cool they would be. Oh, and electronic paper too. And those things had prototypes and everything. And even if they didn't, in 5 years or so a plasma display would only cost as much as a CRT.

Let's fast-forward 7 years to the present and there's an announcement that a lab has created a device, and we translate this to mean that functional products are just around the corner.

Excuse me for being such a cynic, but until something hits store shelves at an affordable price, its pretty pointless to get excited.

Short lifespan

[BESTouff]

However, the efficiency and lifespan of both small molecule and polymer type OLEDs, to date, has been poor for small wavelength emitting compounds

Apparently these displays would have a short lifespan. We would then have disposable screens. That seems a perfect consumer target: cheap, glowing, quickly obsolete.

Re:Short lifespan

[Emperor Shaddam IV]

We would then have disposable screens

With Cadium. Wonderful for the water supply and growing plants. My liver and kidneys can hardly wait. I could always use some more heavy metals in my diet.

mmm, high resolution

[briancnorton]

My roommates in grad school were working on this type of thing, and they were promising resolutions over 300 DPI. That makes me salivate, but I find it funny that for once display technology will be more advanced than image generation technology. (video cards) A 300 DPI, 17" widescreen would be a resolution of something like 4500x2500, or 11 million pixels, compared to 1 or 2 million pixels in a high-res display today. AGP 32X anyone?

OLED's

[Emperor Shaddam IV]

Researchers at MIT have developed a new type of Organic Light emitting Diode (OLED) using Cadmium Selenium Quantum Dots as the electron-hole recombination layer

Great, they contain Cadmium. Yet another device with heavy metals in it to polute our landfills and the environment. At least is doesn't have Mercury in it like Florescent light bulbs do.

A step in the right direction but...

[Drakula]

using quantum dots does not solve the total efficiency problem. The overall efficiency of a LED is the product of the injection efficiency, the extraction efficiency, and the internal quantum efficiency. The inorganic quantum dots will make the internal quantum efficiency large, this is how well the device converts the injected electrons into light. However, the big stumbling block is the injection effeciency, how well the injected current is converted to electron-hole pairs for generating light. When this efficiency is low, a large amount of the applied power is lost to heat. This will need to be overcome as well before OLEDs of any type make as a commercial technology.

Also the cadmium selenide system is known to have lifetime issues. These, and related, materials were the first candidates for blue/green LEDs and lasers but suffered from horrible lifetimes.

Cadmium? No thank you

[freshwat]

We're finally getting rid of extremely toxic cadmium in batteries and now this? Don't these guys learn? They have to engineer over the whole like cycle, including disposal.

Re:wearable computer

[Omkar]

People already pay for the priviledge of sporting corporate logos. The days of human billboards are already here.
I wish I had something funny to say about this, but it's just sad, folks.

For those miss the point

[akincisor]

The point of the article is that they have managed to use an inorganic layer in between just two organic layers and produce a magnitude of light equivalent to earlier efforts with 20 layers. These things have 25 times(!) the power efficiency. This might also be the first commercial application of quantum dots.

In the dark about permanent illumination

[melonman]

I'm trying to get my head around the 'self-luminous' bit. So you can't switch them off? What happens when you shut the lid of your portable and put it in its sack for the night? Does it keep the case warm? If these screens are going to be readable in the same conditions as a newspaper, they are going to need to kick out several watts.

Also, I can think of several options for where the power comes from, and none of them fill me with confidence. It could be radioactive, it could be organic (ie your screen is going to gradually eat itself, or do you pour glucose solution into the VGA socket?)...

Is anyone getting anywhere with passive displays, ie systems which work by reflection not emission, and therefore don't need illuminating at all?

Money answer?

[swb]

I wonder sometimes if "the powers that be" aren't just holding back on some of the new LCD-like display technologies because they've got a lot of money tied up in LCD technology that's just starting to show a return on investment.

And there's the whole recession thing, which has limited sales and maybe curtailed manufacturers' desire to invest in converting plants and equipment to make the new displays.

I know it seems a little conspiratorial, and the answer probably that the technology isn't reliable or mass producable yet, but I still can't help but wonder if the economy picks up we'll see from Apple or someone else not afraid to roll out an expensive 1st gen product and then see it approach commodity levels a couple of years later.

Although I keep asking myself why a 13" LCD TV sells for $800 and a 17" LCD monitor is $500. That's a market contrast I *don't* get, and the explanations I've been given about the cost of tuners and IR control logic don't add up, especially when a tube 20" is $170.

Re:Money answer?

[swb]

But its not a no-cost market to enter. To make some new flat panel technology in mass quantities would take hundreds of million to a billion dollars to get started, not to mention a lead time of at least six months to a year to modify or make new tooling and equipment. It's a high-barrier-to-entry market.

Anyway, my speculation in the parent post was based on the idea that most (all?) of the businesses capable of making the new technology are heavily invested in the old technology. Not only is a new panel technology a high barrier to entry market, but the current market is a high barrier to exit -- you can't just junk many hundreds of billions of dollars worth of equipment for making LCD panels and start a new plant; you have to keep making LCDs until the investment has at least broken even or the loss is acceptable.

If the new techologies were easy, cheap and simple to make, I think you're right, we'd have them by now. But they're at least as hard to make as LCDs (in quantity), and even if there are operational advantages to the new panels the display makers aren't going to junk billions in LCD fabs just like that.

Even though it seems conspiratorial, I still think we're not seeing better flat panel displays in part because the current makers just have too much invested in LCDs, even though they could make new ones.

Re:wearable computer

[The Only Druid]

The truth is, wearable displays will be a huge target marget in the second or third generation of these devices.

A significant amount of money is spent by teenagers and young adults to buy tech gadgets. Just look at the massive amounts spent on video games and personal audio devices [by these demographics].

Now considering the number of people in this group that also go to parties/concerts/raves, I dont think it will be long before your shirt has a wireless hookup so that the DJ at whatever club you're at can project a Geiss/Milkdrop/whatever visualization not just with light, but through your clothes. Imagine being pill'ing and looking around to see the world itself as the visualization?

Also, lets not forget the obligatory link back to the concept of adaptive camoflauge for military/police? Anyone go the url handy?

Re:Thin flat displays are NOT the solution

[Anonymous Coward]

I want glasses with a high resolution display. Perhaps even with seperate displays for each eye, for that nice 3D effect.

Apparently you need a 3D display which is viewable for one person. That sure sounds cool, but it's not what I want, nor would it be very useful to my job, or anybody I work with.

Things I can do with a real display I can't do with your per-eye display:

- look over somebody's shoulder to watch what how they're doing something
- call somebody over to show them what I'm doing
- point to somewhere on the display: "hey Bill, look at this"
- make a presentation to a small group of people
- slap a calibration device on it, so I know the colors are correct
- put 2 next to each other, if I want to work with 2 computers

The advantage of big flat-screens is that they solve some of today's problems without introducing new ones. Maybe when user interfaces have gotten far enough along that sharing displays between other computers and other people is easy, and color calibration is handled, then I'll get some super-glasses. Until then, nothing beats a real screen.

Near 100% efficiency?

[atcurtis]

Maybe every electron-hole combination generates a photon of light but IIRC the direction in which the photon of light travels is random.

That means that at least 50% of the photons are travelling the wrong direction... Perhaps the most optimistic view is that 40% are travelling forwards from the OLED screen, the remainder are absorbed back into the substrate and turned into heat.

Maybe someone would like to correct me...

ttfn

Geez

[mao che minh]

"using Cadmium Selenium Quantum Dots as the electron-hole recombination layer"....."small molecule and polymer type OLEDs"....."Using quantum dots as the emissive layer in OLEDs potentially solves both of these problems since they are inorganic and won't degrade, and they have a theoretical maximum quantum efficiency of near 100%."

I feel like I'm reading the transcript of a conversation between the cyborg and the Reading Rainbow guy on Star Trek.