Printing computer displays and solar cells

November 20, 2013

Organic light-emitting diodes (OLEDs) — shown here in this model of the bus stop of the future — may soon be printed (credit: Fraunhofer IAP/Till Budde)

Printable curved computer displays, TV screens, signs, clothing, fluorescent wallpaper, and flexible solar cells will soon be possible using a new printing process for flexible, organic light-emitting diodes, or OLEDs, say German scientists.

“Almost any surface can be made into a display,” said Dr. Armin Wedel, head of division at the Fraunhofer Institute for Applied Polymer Research IAP.

The first curved OLED screens were demonstrated at this year’s IFA consumer electronics trade show in Berlin.

Inkjet-printing OLEDs

Wedel believes OLEDs are ideally suited to all kinds of lighting, including electronic posters, advertisements, large image projections, and road signs. The scientists worked together with mechanical engineering company MBRAUN to develop a production facility able to create OLEDs as well as organic solar cells on an industrial scale.

The new process uses solutions containing luminescent organic molecules and absorptive molecules respectively, which makes printing them onto a carrier film straightforward. This replaces the current process, which involves vaporizing small molecules in a high vacuum, making it very expensive and limited to laboratory demonstrations.

At the heart of the pilot plant is a robot that controls different printers that 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 homogenous surface that creates a perfect lighting layer.

OLEDs have several advantages over conventional display technologies. Unlike liquid crystal displays they do not require backlighting, which means they consume less energy. Since the diodes themselves emit colored light, contrast and color reproduction are better. The 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.

Wedel said investment is needed for the technology to move forward. “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,” he said.