MANUFACTURINGMATERIALS
Materials give the solar industry a bright future
The emerging solar technology industry faces increased pressure to drive down production costs, increase efficiencies and thus increase competitiveness in the marketplace. Jaime Schmitt, Phil McGraw and Kevin McAloon from Morgan Technical Ceramics look at the growing use of ceramics in solar cell production, which is bringing grid parity for solar power closer than ever before.
C
eramic’s unique physical, thermal and electrical properties make it a reliable,
highly durable and cost-effective material for the harsh environments found in solar cell manufacturing. It is being used to optimise the two key manufacturing processes, silicon wafer and thin film PV.
Increased productivity and efficiency can be achieved through using components made from materials that have a long lifetime despite the harsh manufacturing conditions and do not contaminate the PV cells. Innovative technologies and materials from Morgan Technical Ceramics, such as Pyrolytic Boron Nitride (PBN), are playing a key role, and the continual development of new materials with advanced mechanical properties will lead to further improvements. This article describes the use of ceramic materials in the two main solar cell manufacturing processes being silicon or thin film based.
Crystalline silicon wafer technology The main solar cell technology, which accounts for about 80% of the market, is based on wafers of crystalline silicon. This technology is attractive to manufacturers because crystalline silicon wafers produce efficient cells and the cost of silicon has reduced significantly in the last two years. The first stage is processing polysilicon to create ingots of crystalline silicon.
Accurate temperature measurement In the manufacture of crystalline silicon ingots the
melting process for polysilicon takes four to five days and the furnaces reach a temperature of 1600°C. The temperature of the molten silicon needs to be measured accurately to ensure it is not too high, which wastes energy and increases costs, or too low, in which case the silicon does not melt correctly.
Traditionally thermocouples manufactured with alumina have been used for this temperature measurement, but in some cases they have reacted with graphite in the furnace at the high temperatures required. Now thermocouples made from new materials such as fully stabilized zirconia are being developed especially for high temperature measurements. These can be used in environments up to 2000°C degrees with less reaction with other materials.
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www.solar-pv-management.com Issue VI 2010
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