TVs with the thickness and weight of a sheet of paper will be possible someday as printed electronics technology advances. This technology is already used in organic solar cells and organic light-emitting diodes (OLEDs) that form the displays of cellphones by allowing manufacturers to literally print or roll materials onto surfaces to produce an electronically functional device.

However, one current challenge is in manufacturing 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.

But Georgia Tech researchers have introduced what appears to be a universal 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. The interaction turns air-stable conductors into efficient, low-work function electrodes. The commercially available polymers can be easily processed from dilute solutions in solvents such as water and methoxyethanol, are inexpensive, environmentally friendly and compatible with existent roll-to-roll mass production techniques.

After introducing what appears to be a universal technique to reduce the work function of a conductor in printable electronics, a team led by Georgia Tech's Bernard Kippelen has developed the first completely plastic solar cell. (Source: Georgia Tech)

Bernard Kippelen, director of Georgia Tech’s Center for Organic Photonics and Electronics said, “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.” To illustrate the new method, Kippelen and his peers evaluated the polymers’ performance in organic thin-film transistors and OLEDs and have built a prototype of the first-ever, completely plastic solar cell.

–Ann Steffora Mutschler

By Ed Sperling

Doing Business In 3D
IMEC, the Belgian research house, and Synopsys have teamed up to create 3D vertically stacked chips. This topic has received a lot of attention of late, in large part because analog engineers are nearing open rebellion over the need to keep pushing their technology down each process node. A good analog process can last a decade or more, and just re-doing it to put it on the same chip doesn’t make sense.

The missing piece in all this is the through-silicon via, which has been under development for several years. The collaboration is aimed at speeding the development of TSVs and saving the design world from having to re-do everything at 28nm and 22nm. The thought of analog at 11nm is entirely too much to comprehend.

Greener Marines
Green is sort of a natural color for the U.S. Marines, but you don’t exactly associate Marines with green technology. As it turns out, though, battery life in war is critical. According to an announcement issued by the U.S. Marine Corps, “Reducing resupply needs also keeps Marines safer. Fewer trucks on the road decrease Marines’ exposure to the improvised explosive device and other dangers.”

At least part of the effort is on renewable energy at Marine bases. But experiments by the Marine Corps Warfighting Laboratory are now fusing together off-the-shelf technology for renewable energy and lower energy consumption military equipment. The Laboratory, according to the release, “conducts concept-based experiments and integrates operational concepts with how the Corps operates and fights. Experiments coupled with other research improve the expeditionary warfighting capabilities of the Marine Corps today and far into the future.”

End Of The Roll?
Kimberly-Clark has been closely watching the printed electronics market, according to IDTechEx, a British consultancy working in this market. Kimberly-Clark, which makes a variety of paper-based products such as tissues, says that printed electronics would are very useful in controllable heating and electronic sensing. But there are still a couple of hurdles to work out. First, the price is too high. Second, most of the company’s products are disposable, which makes electronics “just not practical, safe or cost-effective.”