Fundamental Aspects of Silicon Refining

硅是制造太阳能电池的主要材料，占当今光伏（PV）材料市场的90%以上。尽管如此，硅的供应有限和价格高昂已经成为实现该技术成为主要电力生产商的潜力的主要障碍。这主要是因为目前没有以可接受的成本和高生产率生产太阳能级硅（SoG-Si）的专用工艺。在过去的几年里，我们的可持续材料加工研究小组，沿着与其他几个小组一直在努力开发技术，以更低的成本生产SoG-Si相比，今天的工艺。这些研究工作的重点是通过实验工作开发工艺，然后进行优化，以便在尽可能短的时间内达到商业规模。与任何其他发展类似，通常对优化技术至关重要的基本方面没有得到研究，在某些情况下没有详细研究。虽然这项发现补助金，几个硅纯化技术的基本方面将进行调查。特别地，与Si精炼热力学相关的四个主题是令人感兴趣的，并且将被研究（a）杂质（P和B）在固体硅和具有Fe、Cu和Zn的二元硅合金之间的分布，（B）对于含有各种氧化物的炉渣和在一定氧势范围内的炉渣和金属之间的杂质分布的热力学，（c）P和B在Si合金（含Cu、Al）和熔盐之间分配的热力学;（d）二氧化硅在冰晶石基熔盐中的溶解度。这种研究对于支持与开发用于生成SoG-Si的技术相关的先前活动至关重要。此外，这样的基础研究是至关重要的，在创建一个知识库，在相对年轻的领域，高纯度硅处理火法冶金技术。长期利益是通过推进太阳能领域产生清洁能源，并培养几名在材料加工，能源材料和表征领域具有专业知识的研究生和本科生。

Silicon is the primary material for manufacture of solar cells, accounting for over 90 percent of today's market for photovoltaic (PV) materials. Nevertheless, the limited supply and high price of Si have created a major obstacle to realizing the technology's potential for becoming a major electricity producer. This is chiefly because currently there is no dedicated process for production of solar grade silicon (SoG-Si) at acceptable cost and high production rate. In the past several years, our Sustainable Materials Processing Research Group, along with several other groups have been striving for developing technologies that would produce SoG-Si at a lower cost compared to today's processes. Most of the emphasis in such research works has been development of process(es) through experimental work followed by optimization, that will reach commercial scale in the shortest time possible. Similar to any other development, often the fundamental aspects that are essential to optimizing the technology have not been looked into, in details in several cases. Though this discovery grant, the fundamental aspects of several silicon purification techniques will be investigated. In particular, four topics related to the thermodynamics of Si refining are of interest and will be studied (a) distribution of impurities (P and B) between solid silicon and binary silicon alloys with Fe, Cu, and Zn, (b) thermodynamics of impurity distribution between slag and metal for slags containing various oxides and under a range of oxygen potentials, (c) thermodynamics of P and B distribution between alloys of Si (with Cu, Al) and molten salt, and (d) solubility of silica in cryolite based molten salts. This kind of research is essential in supporting the previous activities related to developing a technology for generation of SoG-Si. In addition, such fundamental studies are critical in creating a knowledge base in the relatively young field of high purity Si processing by pyrometalllurgical techniques. The long term benefits are generation of clean energy through advancing solar energy field, and training several graduate and undergraduate students with expertise in the fields of materials processing, energy materials, and characterization.