New world record for solar cell efficiency

SWITZERLAND: Empa scientists have developed thin film solar cells on flexible plastic film with a new record efficiency of 20.4 percent for the conversion of sunlight into electrical energy. The cells are based on so-called CIGS semiconductor (copper indium gallium selenide) that have tremendous potential for the provision of low-cost solar power. Next, the technology will be scaled up from the laboratory scale for various industrial applications.

To solar power can offer low, scientists and engineers have long tried to develop an inexpensive solar cell that can be both highly efficient and easy and produced in large quantities. Now one Empa team led by Ayodhya N. Tiwari managed a (further) break. The researchers were able to increase the efficiency of energy conversion from sunlight to electricity in thin-film CIGS solar cells again on flexible plastic sheets significantly - to a new record of 20.4 percent, a marked improvement compared to the previous record of 18.7 percent, to the same team in 2011 in May had erected.

The research team led by Tiwari has studied and developed for some time various thin-film technologies. Over the years, the laboratory has the efficiency of flexible CIGS solar cells since her first world record of 12.8 percent in 1999 to 14.1 percent (2005), 17.6 percent (2010) and 18.7 percent (2011) can always improve.

The projection of silicon solar cells made ​​up the youngest record is the result of innovative ideas and excellent teamwork, especially by students Adrian Chirila and Fabian Pianezzi. The team succeeded, the properties of the light absorbing CIGS layer, which is applied at reduced processing temperatures to be further optimized. The efficiency of the solar cell was verified by the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg (Germany) - and even exceed the record level of 20.3 percent for CIGS solar cells on glass.

Not only that, he meets even the highest efficiency that can be achieved with polycrystalline silicon solar cells. "We finally did it, with the efficiency of polycrystalline silicon solar cells and CIGS thin-film solar cells on glass to catch up," says Tiwari.

Highly efficient, lightweight and flexible thin-film solar modules are ideal for numerous applications, such as in large solar farms on roofs or facades to portable electronics. They can be produced by roll-to-roll manufacturing process, the opposite of silicon technology enable further cost savings. So you have the potential to make solar power in the near future actually affordable.

"The long series of records in efficiency flexible CIGS solar cells at Empa here shows that thin film solar cells to keep up with the performance of polycrystalline silicon cells can certainly. Now it is time to scale up the technology together with an industrial partner for technical applications, so that we can produce large-area modules, "so Empa director, Gian-Luca Bona. To achieve this, the Empa, together with the company Flisom, a young company that has set the industrialization flexible CIGS solar cells on target.

The research was funded over the years by the Swiss National Science Foundation (SNSF), the Commission for Technology and Innovation (CTI), the Swiss Federal Office of Energy (FOE) and the EU Framework programs.