Protective Polymers Pave Way for Plastic Solar Cell

What appears to be a new universal technique to decrease the work function of a conductor in printable electronics has led to the development of the first completely plastic solar cell.

Bernard Kippelen and scientists at Georgia Institute of Technology have spread an ultrathin layer of a polymer, about 1 to 10 nm thick, on the surface of a conductor to produce a strong surface dipole. The interaction turns air-stable conductors into low-work function, efficient electrodes. The team used commercially available polymers that can be easily produced from dilute solutions in solvents like methoxyethanol and water.

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. (Image: Virginie Drujon-Kippelen).

“These polymers are inexpensive, environmentally friendly and compatible with existent roll-to-roll mass production techniques,” said Kippelen, director of Georgia Tech’s Center for Organic Photonics and Electronics (COPE).

The emerging field of printed electronics technology is anticipated to grow quickly over the next 10 years. However, a major challenge lies in low-cost manufacturing of printed electronics in ambient conditions.

The technology requires conductors, such as calcium, lithium or magnesium, with a low-work function to create light or energy by injecting or collecting electrons. These conductors are chemically very reactive. Once exposed to moisture and oxygen, they oxidize and stop functioning, which is why electronics in solar cells and TVs, for example, need to be covered with a rigid, thick barrier such as glass or expensive encapsulation layer.

Researchers at Georgia Tech have developed the first completely plastic solar cell. (Image: Georgia Institute of Technology)

“Replacing the reactive metals with stable conductors, including conducting polymers, completely changes the requirements of how electronics are manufactured and protected,” Kippelen said. “Their use can pave the way for lower cost and more flexible devices.”

Kippelen’s team evaluated the performance of the polymers in organic LEDs and organic thin-film transistors using their universal technique. They developed the first completely plastic solar cell.

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

For more information, visit: www.gatech.edu