OLEDs Stretch the Limits of Light0

Ernest Beck | Wed Dec 21 2011

From cell phones to television screens, billboards and even designer electronics, OLEDs are everywhere. And it’s easy to see why.

Energy-efficient and long lasting, OLEDs are the go-to light source for a new environmentally aware, post-incandescent era. Already capable of being produced as thin and floppy as a sheet of paper, now scientists are taking existing OLED technology a step further, from bendable to the first fully stretchable OLED.

Form factor

Developed by a team at UCLA led by Qibing Pei, a professor of Materials Science and Engineering, the first fully stretchable OLED was achieved by layering a polymer electrode into a light-emitting plastic that remains conductive even while being pulled and elongated like a piece of chewing gum.

“The main place to use a stretchable OLED is where the form factor makes a difference,” Pei—who has worked in this field for decades—explains. Think fabrics integrated with electronics or robotic skin, video displays that can expand and contract, or embedded medical devices that form and stretch in tandem with human tissue.

You want mechanisms that match the biology, that are more flexible and soft and stretchable like the body itself.

That’s why going beyond flexibility is critical, says John Rogers. As a professor of Materials Science and Engineering in the College of Engineering at the University of Illinois at Urbana-Champaign, Rogers also conducts research in the technology.

“Here you can stretch the OLED like a rubber band,” he says. “You can deform the devices in different ways. You can go into new areas.”

Rogers suggests that bio-integration with embedded medical devices is one promising direction for stretchable OLEDs. “If you think about the contours of the human body, or organs like the heart or brain, they are inherently curvilinear,” he points out. “So if you want to bring devices to bear on human health by integrating them, you want mechanisms that match the biology, that are more flexible and soft and stretchable like the body itself.”

Fold that screen

Stretchable OLEDs also create great potential to improve many of the electronics we use today. Video displays are now rigid, but might soon be able to “crumple like a handkerchief and be pulled out of your pocket when you need it,” says Lawrence Gasman, Co-founder and Principal Analyst at Nanomarkets—a market research firm focusing on energy and electronics enabled by advanced materials.

How about a large roll down display screen for use at home watching movies or projecting images, or a more interactive, high tech and wearable military uniform?

“A field uniform is now quite remarkable with the electronics it has, but they are very heavy, Gasman says. “So if you could build a stretchable OLED display into the fabric it would be much lighter.”

After many years of languishing, OLEDs have finally emerged as a real market, and the opportunities for growth are great.

Already a number of companies are helping to make OLEDs commercially viable in a variety of products, such as Samsung mobile phones and Sony high definition televisions.

“After many years of languishing, OLEDs have finally emerged as a real market, and the opportunities for growth are great,” a report from Nanomarkets concludes.

General Electric regards OLEDs as the environmentally-safe light source of the future, and is developing low-cost manufacturing processes to make ultrathin and flexible OLEDs affordable for everything from wallpaper to window shades, bike lights, and low glare wall dividers.

Cheaper and stronger

Looking ahead, however, a new generation of fully stretchable OLEDs still face some daunting challenges. More time is needed to develop the technology before moving on to marketable products and applications, experts say. Increased stability and overall performance of the material, as well as the cost of production, must be improved before moving to real product design.

For example, Professor Pei’s experiment—involving a two-centimeter square patch with a one-centimeter square area that emitted a sky-blue light—only lasted a few hours in a sealed nitrogen-filled box. “If you took it out of the box,” Pei acknowledges, “it would last only a few minutes.”

Even so, Pei and other scientists and engineers who are pioneering this new era of advanced materials are optimistic about the future of stretchable OLEDs and how the technology can be advanced and translated into viable products that enhance our lives and well-being. “We are working on all these issues,” Pei says. “We are motivated.”

Illustration by Gavin Potenza