Record Makes Thin-Film Solar Cell Competitive with Silicon Efficiency

The copper indium gallium diselenide (CIGS) thin-film solar cell recently reached 19.9 percent efficiency, setting a new world record for this type of cell.

Monday, March 24, 2008

Researchers at the U.S. Department of Energy's National Renewable Energy Laboratory have moved closer to creating a thin-film solar cell that can compete with the efficiency of the more common silicon-based solar cell.

The copper indium gallium diselenide (CIGS) thin-film solar cell recently reached 19.9 percent efficiency, setting a new world record for this type of cell. Multicrystalline silicon-based solar cells have shown efficiencies as high as 20.3 percent. The energy conversion efficiency of a solar cell is the percentage of sunlight converted by the cell into electricity.

"This is an important milestone," said NREL Senior Scientist Miguel Contreras. "The thin film people have always looked for matching silicon in performance, and we are reaching that goal."

CIGS cells use extremely thin layers of semiconductor material applied to a low-cost backing such as glass, flexible metallic foils, high-temperature polymers or stainless steel sheets. Thin-film cells require less energy to make and can be fabricated by a variety of processes. Because of this, they provide a promising path for providing more affordable solar cells for residential and other uses. The CIGS cells are of interest for space applications and the portable electronics market because of their light weight. They are also suitable in special architectural uses, such as photovoltaic roof shingles, windows, siding and others.

Researchers were able to set the world record because of improvements in the quality of the material applied during the manufacturing process, boosting the power output from the cell, Contreras said.

Members of the record-setting team at the National Center for Photovoltaics include Contreras, Ingrid Repins, Brian Egaas, John Scharf, Clay DeHart and Raghu Bhattacharya.

NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by Midwest Research Institute and Battelle.

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