Solar cell design reaches record efficiency

May 22, 2008--German physicists have increased the efficiency of solar cells to 23.2%.

May 22nd, 2008

May 22, 2008--Researcher Bram Hoex and colleagues at Eindhoven University of Technology (TUE; Eindhoven, The Netherlands), together with the Fraunhofer Institute for Solar Energy Systems (Freiburg, Germany) have announced a record efficiency of solar cells from 21.9% to 23.2%.

Hoex, a recent doctoral graduate at Eindhoven, presented the new world record on Wednesday, May 14 at the 33rd 33rd IEEE Photovoltaic Specialists Conference in San Diego, CA. The use of an ultra-thin aluminum oxide layer at the front of the cell enables the efficiency improvement and brings a breakthrough in solar energy one step closer.

An improvement of more than 1% (in absolute terms) may at first glance appear modest, but it can enable solar-cell manufacturers to greatly increase the performance of their products. This is because higher efficiency is a very effective way of reducing the cost of solar energy. The cost of applying the thin layer of aluminum oxide is expected to be relatively low. This will mean a significant reduction in the cost of producing solar electricity.

Ultra-thin
The team was able to achieve the increase in efficiency by depositing a 30 nm layer of aluminum oxide on the front of a crystalline silicon n-type PERL solar cell. This layer has an unprecedented high level of built-in negative charges, through which the normally significant energy losses at the surface are almost entirely eliminated. Of all sunlight falling on these cells, 23.2% is now converted into electrical energy. The previous record was 21.9%, which translates to a 6% relative improvement.

Hoex gained his Ph.D. last week at the Applied Physics department of the TUE with this research. He was supported in the Plasma & Materials Processing (PMP) research group by professor Richard van de Sanden and associate professor Erwin Kessels. This group specializes in plasma deposition of extremely thin layers. The Dutch company OTB Solar has been a licensee of one of these processes since 2001, which it is using in its solar-cell production lines. Numerous solar-cell manufacturers around the world use equipment supplied by OTB Solar.

The ultra-thin aluminum oxide layer developed in the PMP group may lead to a technology innovation in the solar-cell world. Numerous major solar-cell manufacturers have already shown interest.

Solar cells have for years looked like a highly promising way to partly solve the energy problem. The sun rises day after day, and solar cells can conveniently be installed on surfaces that have no other useful purpose. Solar energy also offers opportunities for use in developing countries, many of which have high levels of sunshine. Within ten to fifteen years the price of electricity generated by solar cells is expected to be comparable to that of conventional electricity from fossil fuels. This technology breakthrough now brings the industrial application of this type of high-efficiency solar cell closer. For this reason, part of Hoex's PhD research project was paid for by three Dutch ministries: Economic Affairs; Education, Culture and Science; and Housing, Spatial Planning and the Environment.

For more information on the research, please see the Eindhoven Univeristy news site .

The proceedings paper can be downloaded at the conference website HERE..

--V.C.

More in Research