November 27, 2007

Major Switch For Solar Energy

By: by Larry Rulison, Times Union


ALBANY -- In a small physics lab on the uptown campus of the University at Albany, researchers are trying to develop a new type of solar-electric cell that will be cheaper -- and more flexible -- than a traditional solar cell made from silicon.

About 90 percent of solar cells are made from silicon. But there's a mad dash to make the cells from organic material to reduce the cost and foster wider acceptance of the technology.

The organic solar cells are made of alternatives to silicon such as polymers or plastics.

Solar, or photovoltaic, cells produce an electric current when exposed to light.

Organic materials are those derived from carbon, which is the building block of life. Silicon, made from sand, is the same semiconducting material that is used to make computer chips.

Silicon solar cells cost from $3 to $3.50 for each watt of electrical output they produce. Achieving the same electrical output costs just 40 cents using organic material.

"That's why there is the interest in organics," said Pradeep Haldar, a professor at UAlbany's College of Nanoscale Science and Engineering and director of the school's Energy and Environmental Technology Applications Center.

Haldar said his work on organic solar cells is being funded by NASA, which is seeking ways to make flexible solar cells that can be unfolded in space.

He believes organic solar cells won't replace silicon solar cells, but as the technology is perfected, the former will serve in niche applications such as powering computers for the military in the field or for putting solar cells on clothing or tents.

Haldar isn't the only one in the Capital Region searching for a better way to make solar cells. DayStar Technologies Inc. in Halfmoon is working to develop so-called "thin-film" cells made from a mixture of copper, indium, gallium and diselenide that are flexible like organic cells, but more expensive. It takes $2 worth of material to produce each watt of electrical output.

The downside of organic solar cells is their relative inefficiency. Polymer-based solar cells have an efficiency of less than 5 percent, while solar cells using single-crystalline silicon have an efficiency of nearly 25 percent. That means the polymer cells must cover an area five times the size of solar cells to produce the same amount of energy.

Organic solar cells also don't last as long as traditional solar cells.

"If you expose it to air, it degrades," Haldar said. "That's one of the biggest problems."

Haldar and his team of scientists are working to improve the longevity of organic solar cells by adding copper nanorods to the devices.

Another upstate New York researcher working on organic solar cells is George Malliaras, an associate professor in materials science and engineering at Cornell University in Ithaca who also is director of the school's nanoscale facility.

Malliaras says organic solar cells can be a lot cheaper than silicon solar cells because of the way they can be manufactured, in a roll-to-roll process similar to how a newspaper press works.

"That can bring down the cost substantially," Malliaras said Monday. "If you can produce electronics the same way you produce a newspaper, the costs will plummet."

Malliaras also is working on a new process that makes organic solar cells using a spray-on technique for applying the components of the cell.