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© Solarworld Freiberg
Photovoltaics innovation alliance
Projektinfo 10/2013

Science and industry are developing improved technology building blocks at all manufacturing stages for producing high-efficiency Si-cells and modules.
© Solarworld Innovations

Electron microscope image of a 40-μm-wide contact finger on monocrystalline silicon. Source: Solarworld Innovations
© Solarworld Innovations
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Development of high-efficiency solar cells and modules

Research institutes, photovoltaic producers, system manufacturers and solar industry suppliers are working together to produce more powerful and durable modules in a more efficient manner. In the SONNE project, companies and researchers are optimising the output and production of modules made of crystalline silicon cells, whereby they are covering the entire production chain and are making the new developments ready for production in a short time. With their developments they want to reduce the costs of solar power by a third.

In the “SONNE” project, researchers and developers from ten companies and four research institutes are working to increase the efficiency of models made of crystalline silicon cells in comparison with previous standard modules. At the same time they also want to improve the service life of the modules. Their production shall be further automated at an industrial scale and thus made cheaper. The technology developer Solarworld Innovations is coordinating this research consortium and the German government is funding the cooperation as part of the “Photovoltaics Innovation Alliance”. “We have quite a lot in store. We intend to increase the module output from today’s 240 to 250 watts to considerably more than 300 watts. By achieving longer module service lives and optimised production processes, we intend to reduce the cost of solar power by around a third,” explains Dr Karl-Heinz Stegemann, coordinator of the research project and section head at Solarworld Innovations.

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The aim is to achieve module efficiencies of at least 20% for monocrystalline silicon and 17.8% for multicrystalline silicon. This will make it necessary to optimise all parameters along the process chain: the researchers and developers are improving the process flows as well as the cell and module design, and are selecting optimum materials as well as process stages and technologies. Prototypes are being used to verify their ability to be transferred into practice. The initial results of the research project, which is divided into four sub-projects (see Fig.), are already available.

Better efficiency through narrower contacts

One way to improve the efficiency of solar cells is to print thinner contact lines on the cells. This increases the active cell surface area and reduces the shading. A demonstration system has been developed and begun operation at the specialist mechanical engineering company, Jonas & Redmann. It applies the silver paste for contacting as part of a non-contact, fine line print process. The first pilot production was conducted at the end of 2012 with a 40-μm finger width and 80 fingers. An increase in efficiency of 0.2% was verified on mcSi and cSi highefficiency cells. For a 30-μm finger width and 96 fingers, an increase in efficiency of 0.35% was achieved at the laboratory scale. This was based on a new paste generation that was developed as part of the project. It is planned to implement this on a mass production scale by the end of 2013. With high-efficiency cells with new rear side passivation and fine line printing with a 40-μm line width (see Fig.), an increase in efficiency of 0.35% with a cell efficiency of around 20% was achieved on monocrystalline p-type Cz silicon.

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Project coordination
SolarWorld Innovations GmbH