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Thin Film Solar Cell Efficiency Continues to Improve

By Brian Westenhaus | Tue, 22 January 2013 22:35 | 0

Scientists at Empa, the Swiss Federal Laboratories for Materials Science and Technology, have developed thin film solar cells on flexible polymer foils with a new record efficiency of 20.4% for converting sunlight into electricity.

The new Swiss cells are based on the semiconducting material copper indium gallium (di)selenide (CIGS) that’s already known for its potential to provide cost-effective solar electricity. The technology is currently in scale-up for industrial applications.

Empa’s 20.4% Efficient Flexible Thin Film Solar Cell Sheet
Empa’s 20.4% Efficient Flexible Thin Film Solar Cell Sheet.

Ayodhya N. Tiwari leads the team at Empa’s Laboratory for Thin Film and Photovoltaics. The new record of 20.4% energy conversion efficiency is another improvement over the previous record of 18.7% achieved by the same team back in May of 2011.

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Scientists and engineers have been trying to develop a low-cost solar cell, which is both highly efficient and easy to manufacture with high wattage output to make solar electricity affordable on a large scale.  Tiwari’s team has been investigating and developing various thin film solar cell technologies for some time. Over the years the laboratory has boosted the photovoltaic conversion efficiency of flexible CIGS solar cells time and again, from 12.8% in 1999 – the group’s first world record – to 14.1% in 2005, 17.6% in 2010 and 18.7% in 2011.

The latest in the series of records has been achieved, especially credited to PhD students Adrian Chirila and Fabian Pianezzi, thanks to innovative ideas and excellent teamwork in the lab. The team has succeeded in modifying the properties of the CIGS layer, grown at low temperatures, which absorbs light and contributes to the photocurrent in solar cells.

The Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany independently certified the cell efficiency value for Solar Energy Systems.

The news well may shake up the entire industry, Empa’s new record efficiency for flexible solar cells now even exceeds the record value of 20.3% for CIGS solar cells on glass substrates – and equals the highest efficiencies for polycrystalline silicon wafer-based solar cells.

An understandably triumphant Tiwari exclaims, “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.”  Congratulations are in order!

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Thin film has major advantage over glass substrate, its 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 the standard silicon technologies.

Gian-Luca Bona, the Director of Empa boosts the news with, “The series of record efficiencies for flexible CIGS solar cells developed at Empa demonstrates that thin film solar cells can match the excellent performance of polycrystalline silicon cells. Now it is time for the next step, the scale-up of the technology to cover large areas in a cost-efficient roll-to-roll manufacturing process with an industrial partner.”  For that Empa is collaborating with Flisom, a start-up company involved in industrialization of flexible CIGS solar cells.

It looks like thin film has the potential to enable low-cost solar electricity in the near future. The questions about the installed costs have yet to be addressed, but clearing the 20% efficiency line on an already low cost production method is really going to help.

Now for some cost miracles on the converting the panel output to household and grid specifications, please?

Congratulations to the Swiss.  The Empa research work has been supported over the years by the Swiss National Science Foundation, the Commission for Technology and Innovation, the Swiss Federal Office of Energy and the EU Framework Programs.  One hopes the Chinese manufacturers don’t swipe the technology too soon or readily agree to licensing terms.

By. Brian Westenhaus

Source: http://newenergyandfuel.com/http:/newenergyandfuel/com/2013/01/21/new-world-record-for-thin-film-solar-cell-efficiency/

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