Regular readers know the LED and its organic OLED cousin are getting poised to compete with the compact florescent and incandescent light sources.  The past few days has seen two OLED breakthroughs that are quite similar and worth a very close look.

Current OLEDs are made of glass substrates and encapsulated between two layers of glass to protect them from external factors like moisture.  Researchers both academic and commercial are working towards replacing both the glass substrate and the encapsulation with flexible foils and thin film layers. Success at commercial scale would enable significant reduction of the production costs of OLEDs because the usage of plastics and flexible foils enables high-speed roll-to-roll fabrication.

Beyond the energy savings that LEDs and OLEDs offer, a thinner and flexible lightweight OLED would set up product design to letting any object in a home or office emit light, and even customized light patterns would become much more affordable.

So the research is very worthwhile.  Now two teams are suggesting they have the answer.
Flip a coin to see who goes first  . . .

Beginning in 2005 the Philips Research of the huge Philips company and now 35 other industrial partners have combined their innovation power at Holst Centre in Eindhoven, the Netherlands.  There Paul Blom and Ton van Mol describe a way of creating thin, flexible sheets of organic light-emitting diodes (OLEDs) using a cheap, newspaper-style “roll-to-roll” printing process.

Making Paper Thin OLEDs. Image Credit: Holst Centre. Click image for the largest view.

The bottom layer of a Holst OLED, which acts as a support, is a flexible material such as a polymer foil that has the electrodes and the light-emitting layer sandwiched on top to make up the complete device. Each layer is between 5 and 200 nanometres thick.

Several hurdles that need to be overcome before OLEDs become a commercial commodity, such as depositing the materials onto a thin film sheet with high precision, managing the properties of the different materials and, most importantly, keeping water out of the device – OLEDs have a barrier requirement up to a thousand times more demanding that food packaging.

Blom and van Mol’s paper is due to appear in the November issue of Physics World. (Link not yet available at post date.)  As noted above, with Philips and 35 other industrial firms on the inside track, providing resources, you can be pretty sure the going to scale matter was an early research parameter.

In North America engineering researchers at the University of Toronto, Canada, have developed “the world’s most efficient organic light-emitting diodes” on plastic. The result enables a flexible form factor, not to mention a less costly, alternative to traditional OLED manufacturing on rigid glass.

The Toronto team is going for the dominant technology for advanced electronic screens that are already used in some high-end cell phones and other smaller-scale applications.

Creating the Digital Displays of Tomorrow from U of T Engineering on Vimeo.

Professor Zheng-Hong Lu a materials science and engineering professor and the Canada Research Chair (Tier I) in Organic Optoelectronics said, “For years, the biggest excitement behind OLED technologies has been the potential to effectively produce them on flexible plastic.”

Device Structure of the Flexible OLED. Click image for more info.

The research, which was supervised by Lu and led by PhD candidates Zhibin Wang and Michael G. Helander, demonstrated the first high-efficiency OLED on plastic. The performance of their device is comparable with the best glass-based OLEDs, while providing the benefits offered by using plastic.

An excited Lu said, “This discovery, unlocks the full potential of OLEDs, leading the way to energy-efficient, flexible and impact-resistant displays.”

Wang and Helander were able to re-construct the property previously limited to glass by using a 50-100 nanometre thick layer of an advanced optical thin-film coating material. This advanced coating technique, when applied on flexible plastic, allowed the team to build the highest efficiency OLED device ever reported with a glass-tree design.

The results are reported online in the latest issue of Nature Photonics.

The team believes it has a full potential OLED on flexible plastic and are report high-efficiency phosphorescent OLEDs using a thin-film outcoupling enhancement method that does not depend on high-index substrates.  This too, could be very close to commercially ready.

The OLED is a very pleasant light source and works well, if currently expensive, used in display screens.  Getting to simple lighting needs a very steep drop in costs, and these two teams are well on the way to getting there.

LED and OLED are both much preferable to the harshness of florescent and can fairly be expected to be superior to incandescent too.  Added up lighting uses a lot of electricity and the LED and OLED offer a much less expensive way to light things up.  They can’t come too soon.


1 Comment so far

  1. Matt Musson on November 2, 2011 9:17 AM

    Great. We can take our dodgy old CFL’s to a toxic waste disposal site.

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