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Thin-Film Solar Cell Efficiency Exceeds 20 Percent

DÜBENDORF, Switzerland, Jan. 24, 2013 — Thin-film solar cells on flexible polymer foils, based on copper indium gallium (di)selenide (CIGS), have set an efficiency record of 20.4 percent for converting sunlight into electricity.

This is the fifth consecutive record for scientists at Empa, the Swiss Federal Laboratory for Materials Science and Technology, beating their May 2011 feat of 18.7 percent (See: Flexible Solar Cells Set Efficiency Record).

“We have now — finally — managed to close the ‘efficiency gap’ to solar cells based on polycrystalline silicon wafers or CIGS thin-film cells on glass,” said team leader Ayodhya N. Tiwari.


High-efficiency flexible CIGS solar cells on polyimide film developed at Empa using a novel process. Courtesy of Empa.

Attractive for a variety of applications, the cells boast increased flexibility and a more cost-effective roll-to-roll manufacturing process than standard silicon technologies.

To achieve higher efficiencies, the team modified the properties of the CIGS layer — grown at low temperatures — which absorbs light and contributes to the photocurrent in solar cells. The cell efficiency value was independently certified by the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany. The new efficiency beats the record of 20.3 percent efficiency for CIGS solar cells on glass substrates and equals that of the most efficient polycrystalline silicon wafer-based solar cells.

The next step for the team is to scale-up the technology “to cover large areas in a cost-efficient roll-to-roll manufacturing process with an industrial partner,” said Empa Director Gian-Luca Bona. Empa will collaborate with startup company Flisom to help achieve this.

The research is supported by the Swiss National Science Foundation, the Commission for Technology and Innovation, the Swiss Federal Office of Energy and the European Union Framework Programmes.

For more information, visit: www.empa.ch


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