SOLAR TECHNOLOGY

Low-priced plastic photovoltaics

Solar cells and panels, which tap the power of the sun and convert it to electricity, offer a green - and potentially unlimited - alternative to fossil fuel use. So why haven't solar technologies been more widely adopted?

Quite simply, they're too expensive, Researchers have come up with a technology that might help bring the prices down.

To collect a lot of sunlight you need to cover a large area in solar panels, which is very expensive for traditional inorganic - usually silicon - photovoltaics. The high costs arise because traditional panels must be made from high purity crystals that require high temperatures and vacuum conditions to manufacture energy potential.

A cheaper solution is to construct the photovoltaic devices out of organic compounds - building what are essentially plastic solar cells. Organic semiconducting materials, and especially polymers, can be dissolved to make an ink and then simply "printed" in a very thin layer, some 100 billionths of a meter thick, over a large area.

Covering a large area in plastic is much cheaper than covering it in silicon, and as a result the cost per Watt of electricity-generating capacity has the potential to be much lower.

One major difficulty with doing this, however, is controlling the arrangement of polymer molecules within the thin layer. Scientists have developed an advanced structural probe technique to determine the molecular packing of two different polymers when they are mixed together. By manipulating how the molecules of the two different polymers pack together, they have created ordered pathways - or "nanowires" - along which electrical charges can more easily travel. This enables the solar cell to produce more electrical current.

This work highlights the importance of the precise arrangement of polymer molecules in a polymer solar cell for it to work efficiently. Researchers and scientists expect polymer solar cells to reach the commercial market within 5 to 10 years.