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New nanotech barriers may help lay OLED problems to rest

The fledgling OLED market hold incredible promise in terms of brightness, color, and efficiency, as well as the possibility of flexible displays.  Seeing one of these displays, such as Sony's XEL-1 (the first commercial OLED tv/monitor) in action the difference is noticeable.  Unfortunately the displays are plagued with lifetime issues.  While much of this has been resolved with better designed blue phosphors, traditionally the weakest link, the major problem of water damage remains.

When exposed to water and oxygen, the organic materials in OLEDs corrode quickly.  Even water vapor can ruin an OLED display over time.  Manufacturers have come up with complex sealing processes, but have only been moderately successful in holding back the damage.  Now, researchers have developed a new nanomaterial that may allow for optimal protection for OLEDs, clearing one of the last major roadblocks to their adoption.

Researchers at the Singapore A*STAR’s Institute of Materials Research and Engineering (IMRE) developed a thin nanofilm which promises to protect not only OLEDs, but also components such as solar cells, with a moisture protection level of over 1,000 times anything currently on the market.

The UK Centre for Process Innovation analyzed the barrier and verified that it had the highest reported water vapor barrier performance to date.  The new barrier promises to revolutionize the plastic electronics industry.  Within five years the plastic electronics industry is expected to grow to a $23B USD market worldwide.

Current films typically have a water vapor transmission rate of around 10-3g/m2 at 25°C and 90% relative humidity (RH).  Ideally barriers to organic electronic devices need to be much lower, around a millionth of a gram per square meter per day (10-6g/m2), at a slightly higher temperature of 39°C.  The problems with current materials arise when pinholes, cracks and grain boundaries occur in the thin oxide barrier films deposited on the plastic, leading to ‘pore effects’ which allow water and oxygen molecules to penetrated the barrier plastic.

The current best solution to the pore problem is to alternate layers of organic and inorganic deposited on the plastic.  This causes the pores to be misaligned, creating a "torturous path" for the damaging water and oxygen molecules.  While this approach is reasonably effective, it increases production cost and complexity.  The IMRE researchers instead looked to a novel approach to solving the problem, plugging the holes with nanoparticles.  This reduces the complex multilayer barrier down to a simple, more efficient two layer barrier, with a barrier oxide layer and a nanoparticlulate sealant layer.

The handy nanoparticles used in the seal not only block the path of moisture and oxygen, but they also trap it and react with it, further decreasing transmission.  The barrier let less than 10-6g/m2 of moisture in under testing.  Further the lag time, or the time it took for water to penetrate the barrier, was an astounding 2300 hours (approximately 96 days) at 60°C and 90% RH.   Senthil Ramadas, principal investigator of the IMRE project states, "With a level of protection that surpasses the ideal requirements for such films to date, manufacturers now have the opportunity to extend the lifetime of plastic electronic devices by leaps and bounds!"

One problem the team faced is exactly how to measure permeation of an extremely low permeation barrier.  The team devised an improved water and oxygen pentetration measurement device, that can detect levels of less than 10-8g/m2.  The new test has already been put to use in various service industry projects.  Says Senthil, "Together with our expertise in encapsulation processes and permeation measurement technologies we are also able to provide a total solution package for industries such as flexible solar cells and OLED displays producers."

The research has been funded by Exploit Technologies Pte Ltd (ETPL), the commercialization branch of A*Star, due to its promise.  Boon Swan Foo, the Executive Chairman of ETPL states, “Exploit Technologies sees commercial potential in A*STAR IMRE’s breakthrough barrier film technology. It has excellent promise for enabling the fast growing plastic electronics industry. We want to take this technology from the lab to the market.”

The IMRE research team is already in talks with solar cell, lighting industry, and flexible display manufacturers, it says.  The center has already signed agreements with a number of companies to commercialize the technology, including a collaboration agreement with G24Innovations, a major thin film solar cell company, as well as an agreement with Asian electronics manufacture KISCO. 

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Multiple layers?
By MBlueD on 4/30/2008 1:44:42 PM , Rating: 3
If one layer can be this effective at resisting water vapor, will two layers provide better performance? I'm confused by the fact that the water vapor transmission rate specified is in g/m2, which emphasizes surface area, which means that this material's performance is independent of thickness...

RE: Multiple layers?
By Smartless on 4/30/2008 2:26:38 PM , Rating: 2

This looked interesting. I had thought this nano-particle process was just like the stuff they use in some car waxes to seal the cracks in previous coats but I guess its a biiiiiit more complicated.

RE: Multiple layers?
By 325hhee on 4/30/2008 2:30:49 PM , Rating: 2
If one layer can be this effective at resisting water vapor, will two layers provide better performance? I'm confused by the fact that the water vapor transmission rate specified is in g/m2, which emphasizes surface area, which means that this material's performance is independent of thickness...

The Oled were also designed with two thoughts, to be ultra thin, and some were able to be rolled. Adding another layer would hinder the purpose of the design intent.

I don't know who's idea it is, but I'm more than content with a monitor being 2" thick, they're aiming for less than 1" thickness. Hehe, some people are also thinking sci-fi, no thickness at all, just light emitted into thin air.

By drank12quartsstrohsbeer on 4/30/2008 3:26:40 PM , Rating: 2
if the first oled models cant be rolled up or are as thick as a LCD, I'm OK with that.

Higher pixel density and response time are the main benefits to me.

RE: Multiple layers?
By masher2 on 4/30/2008 4:33:47 PM , Rating: 3
> "The Oled were also designed with two thoughts, to be ultra thin, and some were able to be rolled. Adding another layer would hinder the purpose of the design intent"

These protective films are microns thick; one could add dozens more without noticing the increased thickness from a design perspective.

The issue is primarily manufacturing complexity (which affects cost) and light transmittance.

RE: Multiple layers?
By giraffeofemaus on 5/1/2008 10:04:27 PM , Rating: 2
The "water vapor transmission rate" that is specified is what would more scientifically be referred to as a flux, which is a flow through a unit area. According to Fick's law of diffusion, after a long time the flux will become relatively steady and be equal regardless of the film thickness. If the flux were not the same across the entire film, pools of water would begin to form in the film. The author is largely correct in specifying the mass flux (vapor transmission rate) in terms of g/m^2, although one could reasonably insert a time unit for greater accuracy (e.g. g/(yr*m^2)).

By tastyratz on 4/30/2008 2:10:11 PM , Rating: 2
if the sealing is so unbelievably demanding on an oled display like this that we require it be tight down to the nano level just how robust a system would the oled display be? 1 drop, 1 bump... if you twist the thin fragile casing ever so slightly carrying it in the house will it separate ever so little and cause deterioration?

RE: and
By drank12quartsstrohsbeer on 4/30/2008 3:23:33 PM , Rating: 2
I believe that each pixel is self contained, so if a small breach of the film happens, it will affect the pixel under the breach. Kind of like the dead pixels of an lcd. I think. I'm sure someone will correct me if im wrong.

A thought...
By TimberJon on 4/30/2008 2:22:50 PM , Rating: 2
Perhaps a solution would be to place the screen behind glass and encapsulate the actual screen in another shell, with fans/Etc.. that will constantly maintain a dry atmosphere for the volume within.

Then the screen could be protected from impact AND moisture, to a degree. Even if I were to buy one of those OLED panels, I would draft and build an enclosure for it.

RE: A thought...
By StormEffect on 4/30/2008 5:28:52 PM , Rating: 2
Its a technical solution, but this kind of encapsulation would greatly increase weight and bulk, two things OLEDs are trying to cut down on. So yeah it might prevent damage, but it will also prevent average people actually buying it.

Na... Na... Na...
By Polynikes on 4/30/2008 6:05:03 PM , Rating: 3

*wipes nose*

blah blah blah blah
By noxipoo on 4/30/08, Rating: -1
RE: blah blah blah blah
By Zirconium on 4/30/2008 1:27:19 PM , Rating: 5
i just want to know if there's a date out there to actually buy an affordable OLED display for my PC.
No. Happy?

RE: blah blah blah blah
By Oroka on 4/30/2008 1:48:28 PM , Rating: 2
Straight answer FTW!!!

RE: blah blah blah blah
By Belard on 4/30/2008 2:12:54 PM , Rating: 3
That is what they are working on. OLED display is not just one thing. Its made up of various technology parts.
When LCDs were new, they were expensive, thats why color notebooks from 1997 were about $4000. My 15" LCD was $1200 new from 2000. A 24" display from 2003 was $3500! Today, 22" monitors are $200, 24" are $350~600 and 27" are as low as $500.

It takes time to make these things work. The problems with OLED are being addressed. If you bought an OLED monitor 1-2 years ago, you'd be screaming about the blue dying on you... or that it doesn't last as long as an LCD.

I would love to have an OLED monitor... but it won't be any time soon. I'll be picking up a $400LCD monitor this weekend... And I expect that a 24~27" OLED for under $600 will take another 4-5 years.

RE: blah blah blah blah
By rockyct on 4/30/2008 5:55:19 PM , Rating: 3
OLED displays are going to start hitting the market in the next year or so, but I'd say it'd be closer to 10 years before they completely replace LCDs.

They are beautiful displays though. No backlight so the blacks are black and the viewing angle is almost 180 degrees. There are so many new applications for this technology. Thiner laptops, head's up displays for your car, newspapers a la Minority Report style, real digital picture frames. Heck, you could have thin panels of OLED displays that will replace incandescent/CFL/LED lighting.

"This is from the It's a science website." -- Rush Limbaugh

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