RENEWABLE ENERGY:

Breakthrough reported on low-cost alternative to silicon solar cells

Solar cells could be produced from materials other than silicon under a breakthrough that scientists at the University of California, Los Angeles, say could dramatically reduce the price of solar technologies.

Solar companies have been searching for some time for materials that are more efficient, cheaper to produce and use fewer raw materials than silicon. But tests of copper, indium, gallium, selenide (CIGS) or related materials have failed so far to produce a winner.

"People have already demonstrated efficiency levels of up to 20 percent, but the current processing method is costly," said William Hou, an engineering graduate student at UCLA, in a statement. "Ultimately the cost of fabricating the product makes it difficult to be competitive with current grid prices."

Hou and his colleagues report in this week's Thin Solid Films the development of a low-cost processing method for solar cells made from copper, indium and diselenide. Those cells, they say, will have the potential to be produced on a large scale for a number of applications, including placement on backpacks or clothing.

"With the solution process that we recently developed, we can inherently reach the same [20 percent] efficiency levels and bring the cost of manufacturing down quite significantly," Hou said.

So far, the researchers have achieved 9.13 percent efficiency over the 16-month project, but they are optimistic that they will reach their goal of 15 percent or 20 percent efficiency.

"We started this process 16 months ago from ground zero. We spent three to four months getting the material to reach 1 percent, and today it is around 9 percent," said Yang Yang, a UCLA engineering professor who led the research team. "That is about an average increase of 1 percent every two months."

Most CIGS solar cells are produced using a co-evaporation technique that involves vacuums and can be costly and time-consuming. The elements are heated and deposited on a surface in a vacuum.

But the UCLA team has created its copper-indium-diselenide solar cell without going through the vacuum evaporation process. Instead, they dissolve their material into a liquid, apply it to a surface and bake it. In solution form, their solar absorber layer -- the part made from the copper-indium-diselenide or CIGS materials and critical to the performance of the cell -- can be easily painted or coated onto a surface.

"In our method, [an] advantage is our solution technology has the potential to be fabricated in a continuous roll-to-roll process," Hou said, which is an important cost breakthrough.

Yang said the technology could reach commercial scale in three or four years.

"As we continue to work on enhancing the performance and efficiency of the solar cells, we also look forward to opportunities to collaborate with industry in order to develop this technology further," Yang said.

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