Anti-aging elixir for solar cells

New coating to make photovoltaic modules more durable

Solar cells DOE
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Photovoltaic modules provide electricity without risks and side effects for the environment and the climate. But the solar power is expensive. The modules must therefore last as long as possible. American Fraunhofer researchers have therefore searched for materials that protect solar cells against destructive environmental influences.

Sometimes, a few cents decide on the success or failure of a technology. For example, as long as solar power is more expensive than energy derived from fossil fuels, it is not competitive on the open market. "Electricity generation from solar energy is still dependent on subsidies - in the US this is no different than in Germany, " explains Christian Hoepfner, Scientific Director of the Fraunhofer Center for Sustainable Energy Systems CSE in Cambridge, USA - a subsidiary of the Fraunhofer Institute for Energy Solar Energy Systems ISE in Freiburg. "If we want renewable energies to succeed in the global marketplace for the long term, we need to make sure that they become cheaper."

Patent recipes, how to achieve this goal, does not exist: The efficiency can not be increased infinitely and the production of solar modules is expensive. If you want to change things here, you have to work hard: engineering teams around the world are looking for new techniques and manufacturing methods that make cells and modules cheaper, more effective, more resistant and more reliable.

Coated solar cells tested © Fraunhofer Gesellschaft

Silicones - stable and resilient

Promising materials include silicones. These are highly peculiar substances - hybrids that are related to both crystals and plastics, but can not be properly assigned to any group. The photovoltaic industry has been using silicones for some time to encapsulate modules. However, they have hardly been used for lamination. The lamination is a protective layer surrounding the frangible silicon wafers. Most manufacturers protect the wafers with ethylene vinyl acetate.

To find out if the ethylene vinyl acetate can be replaced by silicone, a team of scientists went to work. The experts doused photovoltaic cells with liquid silicone. "When it hardens, it seals the cells, so the electronic components are optimally protected, " says Project Manager Rafal Mickiewicz. From the cells laminated with silicone, the experts built prototypes on the CSE and tested these photovoltaic modules according to all the rules of engineering: the modules were tested in a climate chamber at low temperatures and cyclic mechanical loads. The engineers then used a flash of light to test the performance of the modules and looked for microcracks using electro-luminescence imaging. display

The comparison of the results with those of conventional solar modules showed that silicone-coated photovoltaic modules better withstand cyclic loads, for example due to strong wind and high temperatures. The tests are now complete and were published at the 26th European Photovoltaic Solar Energy Conference in 2011. "The test results show that silicone lamination is particularly suitable for certain applications because the silicone protects the fragile components inside and also withstands strong temperature fluctuations. For example, with this technology we can make modules with thin silicon solar cells more robust, "says Mickiewicz.

(Fraunhofer Center for Sustainable Energy Systems CS, Cambridge, US-MA / Fraunhofer Society, 05.07.2012 - NPO)