Purple Pokeberries could take us closer to affordable solar power

Pokeberries – the weeds that children smash to stain their cheeks purple- could be the key to
spreading solar power across the globe, according to researchers at Wake Forest
University's Center for Nanotechnology and Molecular Materials.

Nanotech Center scientists have used the red dye made from pokeberries to
coat their efficient and inexpensive fiber-based solar cells. The dye acts as an
absorber, helping the cell's tiny fibers trap more sunlight to convert into
power.

Pokeberries proliferate even during drought and in rocky, infertile soil. They're weeds," Carroll said. "They grow on every continent but Antarctica."

Wake Forest University holds the first patent for fiber-based photovoltaic,
or solar, cells, granted by the European Patent Office in November. A spinoff
company called FiberCell Inc. has received the license to develop manufacturing
methods for the new solar cell.

The fiber cells can produce as much as twice the power that current flat-cell
technology can produce. That's because they are composed of millions of tiny,
plastic "cans" that trap light until most of it is absorbed. Since the fibers
create much more surface area, the fiber solar cells can collect light at any
angle – from the time the sun rises until it sets.

To make the cells, the plastic fibers are stamped onto plastic sheets, with
the same technology used to attach the tops of soft-drink cans. The absorber –
either a polymer or a less-expensive dye – is sprayed on. The plastic makes the
cells lightweight and flexible, so a manufacturer could roll them up and ship
them cheaply to developing countries – to power a medical clinic, for instance.

Once the primary manufacturer ships the cells, workers at local plants would
spray them with the dye and prepare them for installation. Carroll estimates it
would cost about $5 million to set up a finishing plant – about $15 million less
than it could cost to set up a similar plant for flat cells.

"We could provide the substrate," he said. "If Africa grows the pokeberries,
they could take it home.

"It's a low-cost solar cell that can be made to work with local, low-cost
agricultural crops like pokeberries and with a means of production that emerging
economies can afford."
- Wake Forest