冶金法制备太阳能级多晶硅的研究进展

与改良西门子法、新硅烷法、流化床法等化学方法制备太阳能级多晶硅相比,冶金法制备太阳能级多晶硅是解决光伏产业原料供应不足、降低成本的重要途径.阐述了冶金法制备太阳能级多晶硅过程中去除冶金级硅中金属和非金属杂质的基本原理,介绍了冶金法制备太阳能级多晶硅技术的研究进展情况.     

冶金法制备太阳能级多晶硅的热力学研究进展

冶金法制备太阳能级硅是目前多晶硅材料的研究热点。为更深入理解冶金法制备太阳能级硅的原理,本文综述了几种常见的冶金法提纯多晶硅的热力学研究进展,重点对定向凝固过程中杂质的分凝系数问题、真空精炼中杂质蒸气压与温度的关系、以及合金造渣和氧化造渣中杂质的分配规律,以及渣相和硅相体系中各组元的活度测定方法进行了分析,提出了多晶硅热力学研究中尚存在的问题。     

太阳能级多晶硅生产技术发展现状及展望

全面介绍了太阳能级多晶硅的生产技术现状及有代表性的新工艺、新技术的研究动态.太阳能级多晶硅生产技术主要包括西门子法、硅烷法和冶金法.冶金法因工艺简单、投资少、能耗低获得广泛的关注,但目前其产品达不到太阳能级硅的质量要求.展望未来,西门子法仍将是生产高纯度多晶硅的主流技术.     

太阳能级多晶硅定向凝固技术的研究进展

随着太阳能光伏产业在全球范围内的迅猛发展,作为太阳能电池最基础的原材料一高纯多晶硅,在全球范围内严重短缺,迫切需要发展一种高效率低成本的太阳能级多晶硅的制备方法。在各种生产多晶硅的方法中,定向凝固多晶硅因其成本低、环境污染小,工艺相对简单、成熟,且能直接使用冶金级硅为原料的特点,被寄予很大的希望来实现大规模太阳能级硅的生产。本文综合评述近年来太阳能级多晶硅定向凝固技术的研究进展,着重阐述冶金级硅中磷和硼的提纯,以及多晶硅定向凝固组织和缺陷的控制,并提出今后的研究发展方向。     

太阳能电池用多晶硅铸造技术研究进展

高性价比优势使多晶硅成为光伏市场的主要材料.随着太阳能电池向低成本化方向的发展,太阳能电池用多晶硅铸造技术的研究与开发有着重要的意义.综述了目前太阳能电池用多晶硅锭、多晶硅带和多晶硅薄膜的铸造技术的起源、原理、优点和缺点,以及采用不同铸造方法制备的硅组织特点,评述了新的太阳能电池用多晶硅的铸造方法,展望了新的铸造太阳能级多晶硅新技术.     

太阳能电池硅转换材料现状及发展趋势

目前太阳能电池工业转换材料绝大多数都采用硅，而硅材料主要来自于半导体工业的废料。作为硅集成电路和器件用的多晶硅原料的生产普遍采用西门子法。随着光伏产业的迅速发展，来自半导体级硅的废料预计不会明显增加。因此，将不能满足太阳能电池用硅的需求，硅原料已经成为光伏产业发展的最主要的瓶颈之一。为了满足太阳能电池工业健康发展。研究开发一个不依赖于半导体硅生产的低成本太阳能级硅供应体系是非常必要的。     

太阳能级多晶硅冶金法提纯工艺的研究

介绍了太阳能级多晶硅的主要提纯工艺,并提出了冶金法提纯多晶硅的工艺过程,与现在主流的改良西门子法进行提纯效率、成本、耗能以及多环境的影响等方面进行对比。     

冶金硅定向凝固法制备太阳能级多晶硅及其微观组织与位错(英文)

以冶金硅为原料,探索采用具有高温度梯度的真空定向凝固技术制备低成本太阳能级多晶硅,并研究其在不同生长条件下的微观组织特征、晶界与晶粒大小、固液界面形貌以及位错结构。结果表明,当凝固速率低于60μm/s时,能获得具有高密度和良好取向的定向凝固多晶硅棒状试样,硅晶粒大小随凝固速率的增大而减小;在控制凝固过程,获得平的固液界面形貌是获得沿凝固方向排列柱状晶的关键;由于硅的小平面生长特性,微观组织中出现了位错生长台阶和孪晶结构;在晶粒中,位错分布呈现不均匀性,并且位错密度随凝固速率的增加而增加;在此基础上,讨论了多晶硅的生长行为以及位错形成机制。     

等离子体提纯太阳能级硅材料的工艺进展

随着等离子体的发展,利用等离子体的高化学活性进行合金的精炼日益受到重视,等离子体熔炼被广泛应用在材料加工、金属材料提纯精炼等领域.主要介绍了等离子体在制备太阳能级硅方面的应用,以及几种典型的等离子体提纯工艺.     

坩埚表面改性对冶金法多晶硅电学性能的影响

冶金法制备太阳能级多晶硅所用石墨坩埚含有不同类型的金属杂质,这些杂质通常会降低硅锭的电阻率和少于寿命等电学性能.本文研究了坩埚表面改性对冶金法多晶硅电阻率和少子寿命的影响.通过在不同冷凝速率条件下,对工业硅原料在改性前后的坩埚内提纯.经对铸锭切片的电阻率测试得出:坩埚表面改性使冶金法多晶硅锭的电阻率得到了明显的提高,电阻率的最高值由原来冷凝速率为20μ m/s时的110mΩ·cm提高列30μm/s时227mΩ·cm;经对铸锭切片的少于寿命测试得出:冶金法多晶硅的少子寿命在冷凝速率20μn/s时最高,坩埚表面改性使少子寿命由原来的0.81μs提高到1.91μs.     

Siemens and siemens-like processes for producing photovoltaics: Energy payback time and lifetime carbon emissions

Polysilicon photovoltaics will play a significant role in meeting the world’s shortfall in electrical energy this century. The photovoltaic industry relies on high-purity silicon produced in the Siemens process. New Siemens-like processes (which convert metallurgical silicon to trichlorosilane and deposit purified silicon through the decomposition of silane) and metallurgical processes for producing solar silicon are under development. Their energy payback time and lifetime carbon emissions are reviewed. The history of development of Siemens and Siemens-like processes is summarized.     

采用高频磁场去除太阳能级硅熔体中的SiC粒子(英文)

高质量硅材料在光伏太阳能和电子设备中具有重要应用,然而原料中的非金属颗粒和金属杂质严重影响其电学性能和力学性能。由于SiC粒子会降低光伏电池的力学性能并导致分流问题,因此在制备太阳能电池之前必须将这些杂质从硅材料中去除。利用磁场去除液态金属中的非金属杂质是制备高纯金属的一项尖端技术。利用该方法去除冶金级硅材料中的SiC粒子,并结合杂质去除经典模型和计算流体力学对熔体中粒子浓度和分离效率进行计算。为检验该方法的有效性,采用感应炉进行多次实验。结果表明:该方法能有效去除非金属杂质,提纯硅熔体,且实验结果与模型的预测结果相符。     

High-Temperature Refining of Metallurgical-Grade Silicon: A Review

Among currently known alternatives for renewable energy sources, solar power is generally regarded as having the most potential to satisfy the ever-growing demand. While solar photovoltaic power is a well-established technology, its widespread uptake has been hindered by the prohibitively high price of units and thus electricity. This is due mainly to the high cost of the silicon used to fabricate the devices. This article presents a review of the development of established pyrometallurgical techniques as applied to refining metallurgical silicon to solar grade for the purposes of reducing reliance on expensive traditional silicon feedstock. Four basic high-temperature methods??solvent refining, vaporization, electrorefining, and slag treatment??are described, and the limitations and advantages of each method are presented. It is apparent that these techniques are very useful for removing impurities from silicon, but are often selective and not able to remove all problematic elements. Therefore, refining may need to be as a sequence of steps, targeting specific elements each time, or as novel methods combining multiple techniques simultaneously. Ultimately, the successful approach will have to achieve large-scale production by cost-effective means to replace current methods.     

单晶硅切片加工技术研究进展

单晶硅切片加工是集成电路产业和光伏产业的重要环节，其加工方式和加工质量直接影响到晶片的出片率、晶圆衬底和光伏太阳能电池板的生产成本。随着晶片尺寸的不断增大，线锯切片技术已成为目前单晶硅片的主流切片加工技术。为实现单晶硅片高效、精密、低裂纹损伤的切片加工，阐述了线锯切片技术的分类及其加工特点，总结了金刚石线锯切片加工机理的研究现状，探讨了对金刚石线锯切片加工过程的微观分析，概括了单晶硅切片加工引起的裂纹损伤及其抑制措施，指出了单晶硅切片加工技术的发展趋势和面临的挑战。      

Vacuum distillation refining of metallurgical grade silicon （Ⅰ） ——-Thermodynamics on removal of phosphorus from metallurgical grade silicon

The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refining process of the metallurgical grade silicon was studied via separation coefficient of impurity phosphorus in the metallurgical grade silicon and vapor-liquid equilibrium composition diagram of Si-P binary alloy at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined. The results show that the vacuum distillation should be taken to obtain silicon with less than 10^-7 P, and the impurity phosphorus is volatilized easily by vacuum distillation in thermodynamics. Phosphorus is distilled from the molten silicon and concentrated in vapor phase.     

焊接领域发展的新动向——太阳能应用中的焊接及表面工程

阐述了太阳能工业应用的简况,重点介绍了各太阳能电池和太阳能集热器及供热装置中的焊接及表面工程技术,包括:硅太阳能电池的生产链、太阳能电池生产工艺、薄膜太阳能电池、聚光光伏太阳能电池、太阳能集热器及供热装置中的焊接及表面工程技术,最后讨论了几种用于太阳能焊接的可能性。     

High-Purity Composite Briquette for Direct UMG-Si Production in Arc Furnaces

In metallurgical grade Si (MG-Si), the coal (B) and charcoal (P) contents are on average above 30 ppm as the carbon reduction materials used in the arc furnace are either rich in B or in P. A decrease of both impurities by a factor of 3 using purer raw materials would allow for the direct production of the upgraded metallurgical grade (UMG).This would significantly improve the efficiency of the resulting photovoltaic (PV) cells made with the refined solar grade silicon (SoG-Si) or massively decrease the costs of Si purification by shortening the number of steps needed for reaching B and P contents below 1 ppm requested for the SoG-Si used for the PV cells. A composite C/SiO₂ briquette fulfilling the purity targets for the direct production of UMG-Si in the arc furnace was developed. The composite contains several carbon materials with different levels of reactivities and quartz sand. The raw materials aspects, the paste and briquette preparation, as well as the final carbonization step are discussed. The finished briquettes are free of volatiles and are mechanically and thermally very stable, thus, ensuring stable arc furnace charges with minimum losses of dust and SiO gas. Semi-industrial trials including the downstream purification steps for the production of SoG-Si by a metallurgical low-cost route are contemplated.     

Thermodynamics of solar-grade-silicon refining

Solar energy will shortly be in great demand since it is inexhaustible and cleaner than any conventional energy resources. At present, an expensive grade of silicon for semiconductor (SEG-Si) is used for a solar cell to convert solar energy into electricity. However, the amount of supply is limited and we have to develop an innovative process for silicon production with low energy cost in order to spread the solar cell system widely. Using relatively inexpensive metallurgical grade silicon (MG-Si) as a starting material for making solar grade silicon (SOG-Si) is believed to be one of the ways to make solar cells less expensive. Impurities in MG-Si will shorten the lifetime of excited carriers in silicon solar cell and disturb electric generation. Hence, the removal of impurities from silicon is a significant issue in silicon solar cell fabrication. To discuss the possibility and efficiency of the impurity elimination process, evaluation of thermodynamic properties of impurities in molten silicon such as the activity coefficients and the interaction parameters of harmful impurities has been performed.     

Experimental and simulation study for ultrathin (∼100 μm) mono crystalline silicon solar cell with 156×156 mm2 area

A reduction in silicon material consumption in the photovoltaic industry is required for cost reduction. Using crystalline silicon wafers of less than 120 microns of thickness is a promising way for cost and material reduction in the solar cell production. The standard thickness of crystalline silicon solar cells is currently around 180 microns. If the wafers are thinner than 100 microns in the silicon solar cells, the amount of silicon will be reduced by almost half, which should result in prominent cost reduction. With this aim, many groups have worked with thin crystalline silicon wafers. However, most of them have studied with small size substrates. In this paper, we present the electrical characteristics for thin single crystalline silicon solar cells of 100 and 115 μm thickness and 156×156 mm² area manufactured through a conventional process. We have achieved 17.2% conversion efficiency with a 115 μm silicon substrate and 16.8% with a 100 μm substrate. This enables the commercialization of the thin crystalline silicon solar cells with high conversion efficiency. We also suggest issues to be solved in thin crystalline silicon solar cell manufacturing.