Harvesting solar energy from nano-thin films.

• Author: Jean, Grace
• Position: NANOTECHNOLOGY

Researchers at the U.S. Army Soldier Systems Center in Natick, Mass., are developing prototypes of battery chargers and shelters that would harness solar energy through nanocomposite thin-film photovoltaics.

"It's really an exciting time right now, because there are a number of new photovoltaic technologies out there trying to drive down costs, allowing you to use them in ways that couldn't be used before," said Lynne Samuelson, a research chemist at Natick.

Photovoltaic technology has advanced from the large, heavy and expensive glass panels into smaller, lightweight and cheaper devices.

"Up until the last few years, those technologies weren't of interest to the military," said Samuelson. But now, she said, power is a number one priority for soldiers who carry an increasing amount of electronic equipment. They need something lightweight and portable to charge those devices, she said.

Her research team has produced thin-film photovoltaics, or PVs, that could eventually answer that call.

The thin-film PVs are made by coating nanoparticles of titanium dioxide with a light-harvesting dye and sandwiching them between two plastic-based electrodes, said Samuelson. The resulting device has the thickness of three sheets of paper. When light comes through the device, it hits the dye and an electron gets shuttled through the titanium dioxide to the other electrode. A redux mediator keeps the process running, she said.

The sheets of PVs can be cut to any length or width, she said. The longer the device, the more current it will produce. If you need to charge up a radio, for example, you know the watts...