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Roduction of Solar Grade Silicon by Thermal Refining of Industrial Grade Silicon

Fazlali, Reza | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47175 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Yoozbashizadeh, Hossein
  7. Abstract:
  8. The photovoltaic (PV) industry is in rapid growth and a large supply of PV feedstock materials must be provided to maintain this growth. Since silicon is still the dominant material for the fabrication of solar cells, low-cost solar-grade silicon (SoG-Si) feedstock is demanded. The most cost-effective and direct approach for producing SoG-Si is to purify and upgrade metallurgical-grade silicon. The major impurities in silicon are Al, Fe and Ca. other impurities present are Cu, Ti , Zn, Ni, Cr, Mn, Cd, B and P. In this study The effects of the acid leaching process parameters, including the particle size of silicon, the acid type (HCl, HNO3, H2SO4, and their combination), tmepreture and the leaching time on the purification of MG-Siwere investigated. The results show that HCl leaching, an initial size of 125-200 μm for the silicon particles, and 8 h of leaching time at 50 °C are the optimum parameters to purify MG-Si , and The maximum total metallicimpurities removal efficiency was 85% . After acid leaching, metallic impurites in Silicon was separated by process of directional solidification. Molten was moved through sample’s length by speeding 3, 7.5, and 10 mm/min, then value of separation was investigated. Furthermore maximum value of separation in sample’s length took place in speed of 3 mm/min. It should be mention that these process related on purification of Si, and for other elements (B and P) is used other methods
  9. Keywords:
  10. Solar Grade Silicon ; Acidic Leaching ; Directional Solidification ; Solar Cells ; High Purity Silicon ; Metalurgical Grade Silicon

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