Taking Charge of Molecular Wires

Linking single molecules together produces . . . long molecules. Yes, but scientists at Brookhaven view them as much more. They see “molecular wires”  -- tiny electron conductors with huge potential.
— By Laura Mgrdichian

Someday, “molecular wires” may replace silicon in micro-electronic circuits and components in solar energy storage systems. Brookhaven scientists and their colleagues at the University of Florida have uncovered information that may help this happen while studying how electric charge is distributed in polymer molecule chains several nanometers, or billionths of a meter, in length.

“Long molecules that can act as molecular wires, of which there are many variations, are one type of nanoscale object with the potential to lead to new technologies, due to their ability to conduct electricity and very small size,” said Brookhaven chemist John Miller, the study’s lead scientist. “But unlike conventional metal wires, polymer nanowires need assistance in order to conduct.”

“Using a cluster of high-energy electrons from an accelerator, we can quickly add an extra negative or positive charge to a polymer molecular wire,” Miller said. “When the end of the wire contains a chemically-attached ‘trap’ molecule, one where the electrons will be at a lower, more stable energy, the charge moves to it. This allows us to ‘see’ that the wire conducts electrons quickly, and over long distances.”

One potential application for this finding is in the solar energy industry, particularly in a new field called “plastic solar.” In conventional solar cells, incoming solar energy is transferred to the electrons in a semiconducting material, such as silicon, which knocks many of them loose. These electrons are guided to an electrode, creating a current that can be drawn off and used.

The plastic solar movement aims to replace materials like silicon with polymer nano-wires, which are cheaper and lighter. Another advantage of plastic solar cells is their physical versatility. Due to the flexible, bendable nature of polymer materials, plastic solar cells could be placed in areas of greatly varying size and surface type.

Conventional cells are rigid and costly, and the current production method limits their size.