New process promises cheap, flexible electronics

Televisions as thin and flexible as a sheet of paper could be on the way, thanks to a new technique for printing electronics.

At the moment, mass production of such devices is held up by the difficulty of 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.

However, all these are chemically very reactive, oxidizing and stopping working if exposed to oxygen and moisture. As a result, electronics in solar cells and TVs, for example, need a rigid, thick cover such as glass.

However, Georgia Tech researchers have now discovered 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.

“These polymers are inexpensive, environmentally friendly and compatible with existent roll-to-roll mass production techniques,” says Georgia Tech’s Bernard 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.”

The team’s successfully tested the polymers’ performance in organic thin-film transistors and OLEDs – and also built the first-ever completely plastic solar cell.

“The polymer modifier reduces the work function in a wide range of conductors, including silver, gold and aluminum,” says professor Seth Marder. “The process is also effective in transparent metal-oxides and graphene.”