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Materials Technical Papers

  • Cz-Si wafers in solar cell production: Efficiency-limiting defects and material quality control

    Most high-efficiency solar cells are fabricated from monocrystalline Czochralski silicon (Cz-Si) wafers because the material quality is higher than multicrystalline silicon (mc-Si) wafers. However, the material study presented in this paper reveals strong variations in the material quality of commercially available Cz-Si wafers, leading to a loss in solar cell efficiency of 4% absolute. The reason for this is the presence of defects, which appear as dark rings in photoluminescence (PL) images of the finished solar cells. It is shown that these efficiency-limiting defects originate from oxygen precipitation during emitter diffusion. It is demonstrated that an incoming inspection in the as-cut state is difficult, as strong ring structures in as-cut wafers turn out to originate most often from thermal donors. These are dissolved during high-temperature treatments and are therefore harmless, whereas moderate ring structures in the as-cut state may become severe. That is why critical wafers can be identified and sorted out reliably only after emitter diffusion, by using QSSPC-based lifetime measurements or PL imaging. The two-year statistics gathered from the research line at Fraunhofer ISE on the occurrence of ring defects in Cz-Si wafers indicate that ring defects are highly relevant in terms of material yield.

  • Diamond wire sawing: State of the art and perspectives

    The purpose of this paper is to give an overview of the use and potential of diamond wire for the silicon-shaping process in the PV industry. The current market and future prospects for helping to meet the goals of 2020’s roadmap of thinner wafers and reduced $/W are described.

  • PV manufacturing materials: Technological and process-related options for cost reduction

  • Progress in cost reduction in silver pastes for crystalline silicon cells

  • Trace element analysis in crystalline silicon

  • Reducing polysilicon materials costs

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Publications

  • Photovoltaics International 15th Edition

    Photovoltaics International 15th Edition

    The 15th edition of Photovoltaics International hopes to bring some optimism to 2012 by tackling the key factors on how to cope with the current situation. Contributions come from MIT on using TCAD as a viable method for modelling metal impurity evolution; Alternative Energy Investing presents a comprehensive look at materials cost; and efficiency improvements are on offer by ECN. REC Solar and Tata BP Solar report on module lifetime and IMS Research gives us a brief rundown of 2012 global market expectations.

  • Photovoltaics International Lite, Volume 05 - 2011

    Photovoltaics International Lite, Volume 05 - 2011

    This digital interactive Lite sees Tom Cheyney follow Agua Caliente’s progress on becoming one of first truly utility-scale PV power farms, where 40–50MW (AC) will be commissioned by the end of the year. We also feature one of the world’s largest silicon thin-film PV power plants, Avenal; a report on warnings of the collapse of module prices from Solarbuzz and PI-Berlin presents tips on PV module testing. A print version of this edition will be distributed at Solar Power International 2011 in Dallas, Texas.

  • Manufacturing The Solar Future: The 2012 Production Annual

    Manufacturing The Solar Future: The 2012 Production Annual

    Manufacturing the Solar Future 2012, the second in the Photovoltaics International PV Production Annual series, delivers the next installment of in-depth technical manufacturing information on PV production processes.

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