CIGS solar cells boast 20.4% efficiency22 Jan 2013
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To make solar electricity affordable on a large scale, scientists and engineers the world over have long been trying to develop a low-cost solar cell, which is both highly efficient and easy to manufacture with high throughput. Now a team at Empa's Laboratory for Thin Film and Photovoltaics, led by Ayodhya N. Tiwari, has made (yet another) leap ahead. They achieved a record 20.4 per cent energy conversion efficiency for thin film CIGS solar cells on flexible polymer substrates, a massive improvement over the previous record of 18.7 per cent achieved by the same team in May 2011. Over the years the laboratory has boosted the photovoltaic conversion efficiency of flexible CIGS solar cells time and again, from 12.8 per cent in 1999—the group's first world record—to 14.1 per cent in 2005, 17.6 per cent in 2010 and 18.7 per cent in 2011.
The team, which included PhD students Adrian Chirila and Fabian Pianezzi, has succeeded in modifying the properties of the CIGS layer, grown at low temperatures, which absorbs light and contributes to the photo-current in solar cells. The cell efficiency value was independently certified by the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany. What's more, Empa's new record efficiency for flexible solar cells now even exceeds the record value of 20.3 per cent for CIGS solar cells on glass substrates—and equals the highest efficiencies for polycrystalline silicon wafer-based solar cells. "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", indicated Tiwari.
Thin film, lightweight and flexible high-performance solar modules are attractive for numerous applications such as solar farms, roofs and facades of buildings, automobiles and portable electronics and can be produced using continuous roll-to-roll manufacturing processes that offer further cost reductions compared to standard silicon technologies. In other words, they have the potential to enable low-cost solar electricity in the near future.
The technology is currently awaiting scale-up for industrial applications.
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