Research On Metallurgical Processing Of Multi-crystalline Silicon For Solar Cells

Energy, economy and environment are considered as the three main problems of men's continuous development. The shortage of the energy and the deterioration of environment restrict the growing of economy. Solar energy will soon be in great demand since it is inexhaustible and much cleaner than any other conventional energy resources. The photovoltaic industry is growing at the rate of 30% annually. In the near future, the photovoltaic industry will face a severe shortage of crystalline silicon, because the original source, waste from the microelectronic industry, is in decline. So it will be significant to develop a technique with high efficiency and low cost for multi-crystalline silicon making directly from metallurgical-grade silicon which is abundant in China.High-purity multi-crystalline silicon which is the raw material for photovoltaic industry and electronic industry is mainly produced by improved Siemens process during which a mass of silicon alkyl and chloride generated. Even though, the amount of multi-crystalline silicon can not meet the demand of photovoltaic industry. The core technique has not been griped in China. So it is significant to develop a new high-yield and environmental-protective metallurgical process.This project developes a new metallurgical processing combining the vacuum inductive melting technique with directional solidification technique to refine metallurgical silicon. First of all, metallurgical-grade (MG) silicon, the raw material, is melted by electromagnetic inductive heating in vacuum furnace. Then the molten silicon flows to an insulated furnace and solidifies by vacuum directional solidification. Most metalline impurities are segregated towards the top. Finally certain sectional shaped high-purity silicon ingots are obtained.The samples are analyzed by microscope, Electron Probe Microanalysis and Inductive Coupled Plasma.