Fracture of solar-grade anisotropic polycrystalline Silicon: A combined phase field–cohesive zone model approach

Artículo Open Access en el sitio web del editor. Pago por publicar en abierto. This work presents a novel computational framework to simulate fracture events in brittle anisotropic polycrystalline materials at the microscopical level, with application to solar-grade polycrystalline Silicon. Quasi-static failure is modeled by combining the phase field approach of brittle fracture (for transgranular fracture) with the cohesive zone model for the grain boundaries (for intergranular fracture) through the generalization of the recent FE-based technique published in [M. Paggi, J. Reinoso, Comput. Methods Appl. Mech. Engrg., 31 (2017) 145–172] to deal with anisotropic polycrystalline microstructures. The proposed model, which accounts for any anisotropic constitutive tensor for the grains depending on their preferential orientation, as well as an orientation-dependent fracture toughness, allows to simulate intergranular and transgranular crack growths in an efficient manner, with or without initial defects. One of the advantages of the current variational method is the fact that complex crack patterns in such materials are triggered without any user-intervention, being possible to account for the competition between both dissipative phenomena. In addition, further aspects with regard to the model parameters identification are discussed in reference to solar cells images obtained from transmitted light source. A series of representative numerical simulations is carried out to highlight the interplay between the different types of fracture occurring in solar-grade polycrystalline Silicon, and to assess the role of anisotropy on the crack path and on the apparent tensile strength of the material. Unión Europea FP/2007–2013/ERC 306622 Ministerio de Economía y Competitividad MAT2015–71036-P y MAT2015–71309-P Junta de Andalucía P11-TEP-7093 y P12-TEP- 105

Research on Boron Removal Processes for the Production of Solar Grade Polycrystalline Silicon by Metallurgical Methods and Its Controlling Mechanism

硅作为全球半导体工业和光伏产业的基石，一直是太阳能电池的主要原材料。与传统的西门子法制备高纯硅相比，冶金法具有成本低、能耗小、安全环保等优点，因此，为适应太阳能电池产业迅速发展的需求，世界各国都在努力开发新的冶金法制备太阳能级多晶硅工艺。 硼作为硅的受主杂质，在太阳能电池基体中的含量不得高于0.3ppmw。由于硼具有较高的分凝系数和较低的饱和蒸汽压，难以通过传统的定向凝固和真空冶炼去除。本文围绕冶金法制备太阳能级多晶硅除硼的关键技术，开展了以下两方面的工作：首先，从湿法冶金工艺出发，通过熔盐电解精炼金属硅达到有效去除硼杂质的目的，对该方法的可行性和热动力学机理进行了研究；其次，从火法冶金工艺...As the foundation of the global semiconductor and photovoltaic industry, silicon is the main raw material for solar cell. To meet the needs of the rapid development of solar cell industry, all the countries in the world are working to develop new metallurgical methods for the production of solar grade polycrystalline silicon due to its low cost, low energy consumption, safety and environmental pro...学位：工学博士院系专业：材料学院材料科学与工程系_材料学学号：2072007015345

电磁感应辅助等离子体熔炼去除金属硅中的硼

采用自主设计的转移弧等离子体发生装置,对金属硅进行电磁感应加热辅助等离子体熔炼除硼的研究;探索不同工艺条件如反应气体、熔炼时间和初始硼含量对除硼效果和硅损失的影响。结果表明:采用氩气和水蒸气混合气体(Ar+H2O)作为反应气体比氩气和氧气混合气体(Ar+O2)具有更好的除硼效果;随H2O含量的增加,硼的去除率与硅损失率都呈线性增加;采用Ar+1.5%H2O(体积分数)等离子体时,硼的去除率在30 min后达到最大值,其含量从22×10 6降至0.2×10 6(质量分数),硅损失率约为0.5%/min;初始硼含量对除硼效果和硅损失率基本无影响

Manufacture of Granular Polysilicon from Trichlorosilane in an Internally Circulating Fluidized Bed Reactor

A lab scale internally circulating fluidized bed (ICFB) with a centrally located draft tube was designed to make polysilicon from trichlorosilane. Experimental results and evaluations showed that particle circulation could carry enough heat for reaction and effectively decrease wall deposition. Well grown granular polysilicon was obtained in a stable fluidization state and particle circulation rate

A PERSPECTIVE ON DEVELOPMENT OF NOVEL FLUIDIZED BED PROCESSES FOR A MORE SUSTAINABLE GLOBAL FUTURE

Faced with the need for transformative changes to solve global problems, fluidization could play a major role in contributing in areas like carbon capture, use of renewable resources, and recovery of valuable materials from waste streams. Some current examples are discussed where the fluidization community can help to find solution

Design and Process control of Siemens polysilicon CVD reactor

The novelty in this paper is to develop a process control for the poly-silicon CVD reactor to achieve optimum productivity of Poly-silicon seed by controlling the process parameters. The production of ingot is done through Siemens process of decomposing Trichlorosilane by Chemical Vapor Deposition on slim tungsten rods. The hardware architecture proposed monitors and controls the systematic sequential stages furnishing dynamics of the plant at a high temperature around 1050°C-1100°C. The HMI communicates through NI's LabVIEW 8.6 package, alarming the user with Process mimic, Report generation, Data and Security management. The plant simulation is realized and verified with LabVIEW 8.6 Version and MATLab 7.5 software tools to obtain the effectiveness of proposed control technique. This GUI based SCADA handles likelihood of fault tolerance, ensuring risk controlled process with optimum productivity of poly-silicon by making system compliant to Industrial standards

Thermal shields for heat loss reduction in Siemens-type CVD reactors

The use of thermal shields to reduce radiation heat loss in Siemens-type CVD reactors is analyzed, both theoretically and experimentally. The potential savings from the use of the thermal shields is first explored using a radiation heat model that takes emissivity variations with wavelength into account, which is important for materials that do not behave as grey bodies. The theoretical calculations confirm that materials with lower surface emissivity lead to higher radiation savings. Assuming that radiation heat loss is responsible for around 50% of the total power consumption, a reduction of 32.9% and 15.5% is obtained if thermal shields with constant emissivities of 0.3 and 0.7 are considered, respectively. Experiments considering different thermal shields are conducted in a laboratory CVD reactor, confirming that the real materials do not behave as grey bodies, and proving that significant energy savings in the polysilicon deposition process are obtained. Using silicon as a thermal shield leads to energy savings of between 26.5-28.5%. For wavelength-dependent emissivities, the model shows that there are significant differences in radiation heat loss, of around 25%, when compared to that of constant emissivity. The results of the model highlight the importance of having reliable data on the emissivities within the relevant range of wavelengths, and at deposition temperatures, which remains a pending issue

Polycrystalline silicon material availability and market pricing outlook study for 1980 to 88: January 1983 update

Photovoltaic solar cell arrays which convert solar energy into electrical energy can become a cost effective, alternative energy source provided that an adequate supply of low priced materials and automated fabrication techniques are available. Presently, silicon is the most promising cell material for achieving the near term cost goals of the Photovoltaics Program. Electronic grade silicon is produced primarily for the semiconductor industry with the photovoltaic industry using, in most cases, the production rejects of slightly lower grade material. Therefore, the future availability of adequate supplies of low cost silicon is one of the major concerns of the Photovoltaic Program. The supply outlook for silicon with emphasis on pricing is updated and is based primarily on an industry survey conducted by a JPL consultant. This survey included interviews with polycrystalline silicon manufacturers, a large cross section of silicon users and silicon solar cell manufacturers