Purificação de silicio metalurgico por fusão zonal horizontal em forno de feixe de eletrons / Purification of metallurgical silicon by horizontal zone melting in an electron beam furnace

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The search for renewable energy sources has caused a boom in the production of solar cells in this decade, which rose from 0.3 GW in 2002 to 6.0 GW in 2008, totaling 37 billion dollars in 2008. The production of Electronic Grade Silicon (SiGE) increased 127% from 2007 to 2008, and approximately 90% of solar cells produced nowadays use SiGE, which is responsible for 1/4 of the total installation cost of a solar panel. The Siemens process is used all over the world to purify silicon. It is based on the chlorination of silicon and has the disadvantage of generating highly toxic chemical waste. This process produces high-purity silicon with less than 1 ppm impurities, called Electronic Grade Silicon (SiGE). It is used by the microelectronics industry and in the production of solar cells as well. There are two alternatives to meet the demand for silicon for the photovoltaic area. The first one, called Solar Grade Silicon (SiGS), aims to develop a chemical processes, derived from the Siemens process, to produce lower-quality silicon at lower costs, but which still meets the requirements for solar cell manufacture. The second alternative is to try to adapt the metallurgical purification steps of metallurgical grade silicon (SiGM) to obtain silicon that meets SiGS requirements, which is the focus of this work. The possibilities of insertion of Brazil in the photovoltaic market are very large because, besides having the largest quartz reserves in the world, it is the third largest producer of metallurgical silicon in the world and exports it at about U$ 1/kg. However, the aggregation of technology in silicon purification increases its value exponentially, reaching U$100/kg for electronic grade polycrystalline silicon and up to U$ 4.000/kg for layers of mono and polycrystalline silicon, with the same purity. The Department of Materials Engineering of Unicamp has researched SIGS since 1980, having obtained an ingot with 170 ppm metallic impurities in its purest region by acid leaching and unidirectional solidification of SiGM at that time; solar cells with 4% efficiency were produced from this ingot at the Institute of Physics at Unicamp. (...continue)

ASSUNTO(S)

silicio fusão zonal zone melting silicon purification solar cells silicio - purificação celulas solares

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