Ultrapurification of Silicon for Photovoltaic Applications

The recent explosive growth of Photovoltaics and the relative avidity for silicon of the predominant solar cell technology have resulted in a dramatic change of the polysilicon industry structure. While in the past the polysilicon was manufactured almost exclusively for the semiconductor industry, now more than half of the market is devoted to the solar industry. The different alternative routes to purify silicon for photovoltaic applications are presented in the paper, analysing their advantages and drawbacks. Emphasis is made on the CENTESIL initiative, a new private-public partnership venture promoting a pilot plant that is in an advanced state of construction. The goal is to allow the photovoltaic companies worldwide to count with an independent research centre to help them to establish their own polysilicon plant

On track for solar grade silicon through a Siemens process-type laboratory reactor: operating conditions and energy savings

Polysilicon cost impacts significantly on the photovoltaics (PV) cost and on the energy payback time. Nowadays, the besetting production process is the so called Siemens process, polysilicon deposition by chemical vapor deposition (CVD) from Trichlorosilane. Polysilicon purification level for PV is to a certain extent less demanding that for microelectronics. At the Instituto de Energía Solar (IES) research on this subject is performed through a Siemens process-type laboratory reactor. Through the laboratory CVD prototype at the IES laboratories, valuable information about the phenomena involved in the polysilicon deposition process and the operating conditions is obtained. Polysilicon deposition by CVD is a complex process due to the big number of parameters involved. A study on the influence of temperature and inlet gas mixture composition on the polysilicon deposition growth rate, based on experimental experience, is shown. Moreover, CVD process accounts for the largest contribution to the energy consumption of the polysilicon production. In addition, radiation phenomenon is the major responsible for low energetic efficiency of the whole process. This work presents a model of radiation heat loss, and the theoretical calculations are confirmed experimentally through a prototype reactor at our disposal, yielding a valuable know-how for energy consumption reduction at industrial Siemens reactorsPostprint (published version

Progress on optimization of the solar cell fabrication process by impurity-to-efficiency predictive simulator

To optimize the last high temperature step of a standard solar cell fabrication process (the contact cofiring step), the aluminium gettering is incorporated in the Impurity-to-Efficiency simulation tool, so that it models the phosphorus and aluminium co-gettering effect on iron impurities. The impact of iron on the cell efficiency will depend on the balance between precipitate dissolution and gettering. Gettering efficiency is similar in a wide range of peak temperatures (600-850 ºC), so that this peak temperature can be optimized favoring other parameters (e.g. ohmic contact). An industrial co-firing step can enhance the co-gettering effect by adding a temperature plateau after the peak of temperature. For highly contaminated materials, a short plateau (menor que 2 min) at low temperature (600 ºC) is shown to reduce the dissolved iron

Improving up-conversion with PBS quantum dots

This paper evaluates the enhancement of the up-conversion phenomena by combining rare-earth doped phosphors with PbS quantum dots (QDs). We present results on the characterization of two different ways of adhering the up-converter with this fluorescent material to bifacial solar cells: by dissolving the powder in a spin-on oxide and by dissolving it in a silicone gel. The improvement in photocurrent detected for both the oxide and silicone alternatives when including the QDs is 60% better than without them. It is shown that the absorption and emission characteristics of the PbS QDs embedded in oxide and silicone can be tuned into to the desired spectral region. Keywords: quantum dots, up-converter, solar cel

Heterogeneous data source integration for smart grid ecosystems based on metadata mining

The arrival of new technologies related to smart grids and the resulting ecosystem of applications andmanagement systems pose many new problems. The databases of the traditional grid and the variousinitiatives related to new technologies have given rise to many different management systems with several formats and different architectures. A heterogeneous data source integration system is necessary toupdate these systems for the new smart grid reality. Additionally, it is necessary to take advantage of theinformation smart grids provide. In this paper, the authors propose a heterogeneous data source integration based on IEC standards and metadata mining. Additionally, an automatic data mining framework isapplied to model the integrated information.Ministerio de Economía y Competitividad TEC2013-40767-

Socrates thematic network to enhance European teaching of operations and supply chain management: goals, tasks and preliminary results

The EurOMA-sponsored THENEXOM network has been approved by the European Commission through its Socrates community action programme. THENEXOM’s short-term goal is to analyse the present state of Operations and Supply Chain Management in European universities and to identify strengths and weaknesses in order to instigate the use of better practices. A census is being drawn up of OM teachers throughout the 24 countries (and 27 universities) making up the network. A survey can then be taken of the teaching-staff, content and methods employed. The network’s medium-term aim is to tighten links between teaching, research and business practice by reducing imbalances. In compliance with EU recommendations, strategic connections are being sought with America and Asia to expand aforesaid objectives and actions throughout the world.La red THENEXOM, promovida por EurOMA, ha sido aprobada por la Comisión Europea (programa de acción comunitaria Sócrates). Su objetivo a corto plazo es estudiar la situación de la Dirección de Operaciones y la Gestión de Cadenas de Suministro en las universidades europeas, buscando identificar fortalezas y deficiencias y promover el empleo de las mejores prácticas. Para ello se está elaborando un censo de docentes de DO en los 24 países representados en la red (por 27 instituciones universitarias); éste permitirá el desarrollo de una encuesta sobre profesorado, contenidos y metodología docente. A medio plazo, la red ha de servir para estrechar vínculos entre enseñanza, investigación y práctica empresarial, limando los posibles desfases. Siguiendo las recomendaciones de la UE, se están realizando conexiones estratégicas con América y Asia para extender los objetivos y actuaciones mencionados