Imagine owning a television with the thickness and weight of a sheet of paper. Some day in the near future, it will be possible, thanks to the growing field of printed electronics.
The process, which allows manufacturers to print or roll materials onto surfaces to produce an electronically functional device, is already used in organic solar cells and organic light-emitting diodes (OLEDs) that form the displays of cell phones. Batteries, antennas, memories, sensors and other electronic components can also be printed.
This emerging technology is expected to grow by tens of billions of dollars over the next decade. Engineers at the Georgia Tech Center for Organic Photonics and Electronics (COPE) are at the forefront. The nine-year-old R&D facility specializes in creating flexible materials and devices for use in information technology, telecommunications, energy and defense applications.
“A major focus for innovation at COPE is the synthesis of new organic and hybrid compounds to further improve the performance of optoelectronic devices in the field of printed electronics,” says Bernard Kippelen, COPE director and a professor in the School of Electrical and Computer Engineering.
“These material discovery efforts are integrated with studies that focus on the processing, coating and patterning of the new materials using various vacuum deposition techniques, or coating and printing techniques that can be easily scaled up and moved rapidly into production,” adds Kippelen.
“We believe that developing new inks for today’s printed electronic manufacturing industry has value, but are convinced that our mission goes beyond that,” Kippelen points out. “We also work on the packaging of flexible printed electronic devices, an area of research that is often overlooked.”
COPE currently includes 35 faculty members from seven different colleges at Georgia Tech. They interact with 90 undergrads, 40 graduate students and 25 research scientists.
“By making COPE a focal point for campus-wide efforts in the field and including faculty, researchers and students from seven different schools, we leverage a range of expertise that includes chemical, electrical, mechanical and materials engineering,” explains Kippelen. “This allows us to address many of the science and engineering challenges of the emerging technologies in this field.”
Kippelen and his colleagues are currently involved a number of research projects that are sponsored by both public and private funding. Research areas include organic and hybrid photovoltaic technologies, OLEDs for solid-state lighting and displays, organic materials for all-optical switching, and printable organic field-effect transistors for flexible electronics.
One challenge that COPE is tackling is manufacturing flexible electronics at low cost in ambient conditions. In order to create light or energy by injecting or collecting electrons, printed electronics require conductors—usually calcium, magnesium or lithium—with a low-work function.
These metals are chemically very reactive. They oxidize and stop working if exposed to oxygen and moisture. This is why electronics in solar cells and TVs, for example, must be covered with a rigid, thick barrier such as glass or expensive encapsulation layers.
The Georgia Tech engineers have developed a technique to reduce the work function of a conductor. They spread a very thin layer of a polymer, approximately one to 10 nanometers thick, on the conductor’s surface to create a strong surface dipole.
“These polymers are inexpensive, environmentally friendly and compatible with existent roll-to-roll mass production techniques,” says Kippelen. “Replacing the reactive metals with stable conductors, including conducting polymers, completely changes the requirements of how electronics are manufactured and protected. Their use can pave the way for lower cost and more flexible devices.”
Kippelen and his colleagues evaluated the polymers’ performance in organic thin-film transistors and OLEDs. They have also built the world’s first fully plastic solar cell.