The metallurgical method is gradually becoming the mainstream technology for polysilicon production

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According to Business News on November 18, in the rapidly developing photovoltaic industry, polysilicon with a purity of over 7N cannot be used directly to manufacture solar cells; as a result, processes for directly producing 6N solar-grade polysilicon have begun to be explored. On November 18, at the \"2010 China Polysilicon Production Technology and Industrialization Promotion Conference\" organized by China Chemical Industry News, Shi Jun, president of Shanghai ProNew Energy Co., Ltd., said that to obtain high-purity silicon using the Siemens method, it is necessary to add boron or phosphorus to achieve a purity level of 6N before it can be used, which means double waste of energy. 　　According to Shi Jun, the main production processes for directly manufacturing solar polysilicon include the metallurgical method (physical method), zinc reduction method, sodium reduction method, and direct reduction of high-purity silica. Among them, the metallurgical method is the one that has been most explored to date, and it also holds the best prospects for large-scale production. It is estimated that in 2010, the global production capacity of metallurgical polysilicon on an industrial scale will be around 6,900 tons, with actual production amounting to about 3,200 tons. 　　Since 2008, the industrial development of metallurgical solar-grade polysilicon has progressed rapidly, but it faces many problems. Shi Jun explained that the first issue is the unsatisfactory purity. The large-scale production of polycrystalline silicon by metallurgical methods cannot currently guarantee a purity level of 6N (the qualification rate for good manufacturers is around 50%–60%), which results in lower conversion efficiencies for the solar cells produced, at approximately 15%. Secondly, the presence of impurities such as boroxine and boroferrite complexes causes attenuation in metallurgical polysilicon. Third, the quality stability needs further improvement. 　　With the continuous improvement of metallurgical processing technologies, Shi Jun is optimistic, stating that the slicing rate is expected to exceed 70% in the first quarter of 2011, while battery efficiency could surpass 17% by the end of 2011. The degradation of polycrystalline silicon produced by metallurgical methods has been reduced from 25% to below 3%, and this degradation can also be reversed during use. As the scale of industrialization grows larger, the problem of quality inconsistency will also continue to improve. 　　According to Shi Jun, the Ningxia Sun Mountain photovoltaic power plant, which is invested in and operated by Shanghai Pro, began generating electricity on the grid in the first half of this year. The power plant uses metallurgical polysilicon cells throughout, with an average conversion efficiency of 14.5%, and its total installed capacity is 1.05 megawatts.