The SolarFocus project
Higher solar cell efficiency through optimised material utilisation
With an annual global growth rate of more than 30 percent, power generation from sunlight has developed into a substantial industrial sector over the last 10 years. More than 90 percent of all solar cells are made from the semiconducting material silicon.
The German industry leads the international fields of solar cell production and plant engineering. In order to further augment and consolidate the position, 12 enterprises from the German solar energy industry have united with 12 research partners for the joint project Solar Silicon Reseach Cluster SolarFous.
The project itself is sponsored by the German Federal Ministry for Environment, Nature Conservation and Nuclear Safety (BMU), and its goal is to gain a better comprehension of the silicon material used in solar cell manufacturing. Research on the principal mechanisms of silicon processing—which might influence defect behaviour significantly—will be performed under industrial conditions. The BMU will support the project over a three-year period with 4.1 million Euro, and the industry will contribute another 1.2 million Euro, in addition to payments in kind exceeding this amount by far. Through its total of more than 5,000 employees in the photovoltaic sector and an accumulated annual revenue of 2.5 billion Euro in 2006, the participating companies will represent the major part of the solar energy industry based in Germany.
The project will focus on three areas: defect analysis, correlation experiments, and defect engineering and is designed to gain a better insight into the principal mechanisms of silicon crystallisation and further processing of silicon wafers under industrial framework conditions. The project partners expect the results to be innovative approaches to improvements in the fabrication of silicon wafers and optimised solar cell production.
Defect analysis—as one of the focal areas—examines the silicon material currently used for solar cell production. The project partners will be using numerous specialised methods for material analysis. For easier identification and analysis of poor material quality, they will, for instance, apply large-surface, imaging-providing measuring methods—like electroluminescence (EL) or light beam induced current (LBIC)—together with local examinations of material segments such as the transmission electrons microscope (TEM). Supplementing these techniques with additional analytical methods—such as synchrotron radiation—will allow researchers to gain microscopic insights into the chemical composition and to characterise defect structures in an optimum manner.
The next step will focus on correlation experiments during which silicon is deliberately doped with impurities—as they also occur in the manufacturing process--during crystallisation. Based on the research of individual contaminations, the main purpose is to detect the interaction of several simultaneous contaminations, which is done with the methods used in defect analysis.
Finally, in defect engineering the project partners want to apply the knowledge gained from the interaction of defects within new approaches to crystallisation and processing of silicon. The expected results are innovative strategies which will help avoid or passivate electrical defects in solar cell fabrication.
The main goal of of the project SolarFocus is to increase solar cell efficiency leading to cost reductions in solar cell production across the entire value chain through a comprehensive understanding of the defects in silicon. Based on its innovative approach, the project will thus also meet the cost reduction requirements of the Renewable Energy Sources Act.