Organic lights and solar cells straight from the printer

Time is slowly running out for bulky television sets, boxy neon signs and the square-edged backlit displays we all know from shops and airports. It won’t be long before families gathering together to watch television at home will be calling out: “Unroll the screen, dear, the film’s about to start!” And members of the public may soon encounter screens everywhere they go, as almost any surface can be made into a display.

“These may just be ideas at the moment, but they have every chance of becoming reality,” says Armin Wedel from the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam-Golm. But the potential offered by this technology extends beyond screens and displays for consumer electronics, according to Dr Wedel. He believes OLEDs are also suitable for all kinds of lighting and digital signage applications – from advertising hoardings to road signs.

Working with an industry partner, the Fraunhofer team has developed a production facility that has the potential to create OLEDs, as well as organic solar cells, on an industrial scale. They have shown that it is now possible to print OLEDs and solar cells from solutions containing luminescent organic molecules and absorptive molecules respectively, which makes printing them onto a carrier film very straightforward. Hitherto, printing has involved the costly process of vaporisation in a high vacuum. Dr Wedel again:

“We’re now able to produce organic components under close-to-real-life manufacturing conditions with relative ease. Now, for the first time, it will be possible to translate new ideas into commercial products.”

At the heart of the pilot plant is a robot that controls different printers which basically act like an inkjet printing system. OLEDs are applied to the carrier material one layer at a time using a variety of starting materials. This produces a very homogenous surface that creates a perfect lighting layer. According to Wedel, it will be possible to apply the organic electronic system to customers’ specifications, as is currently possible with digital printing.

OLEDs have several advantages over conventional display technologies. Unlike liquid crystal displays they do not require backlighting, which means they consume less energy. Moreover, the contrast and colour reproduction are superior. Electroluminescent displays also offer a large viewing angle of almost 180 degrees, and because they require no backlighting, they can be very thin, making it possible to create entirely new shapes.

There are still several challenges to be met before OLEDs become firmly established on the market. “The main hurdle, as far as I’m concerned, is the high level of investment required to set up manufacturing,” says Dr Wedel.

This is why - at least where lighting is concerned - he expects OLEDs to complement rather than replace conventional lighting devices. His view of where OLED production technology could head is less modest: “My vision is that the day will come when all we need do is switch ink cartridges in our printers in order to print out our own lighting devices.”