PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS Prog. Photovolt: Res. Appl. 2006; 14:513–531 Published online 2 May 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/pip.690 Chemical Natures and Distributions of Metal Impurities in Multicrystalline Silicon Materials T. Buonassisi 1 , A. A. Istratov 1 * ,y , M. D. Pickett 1 , M. Heuer 1 , J. P. Kalejs 2 , G. Hahn 3 , M. A. Marcus 4 , B. Lai 5 , Z. Cai 5 , S. M. Heald 6 , T. F. Ciszek 7 , R. F. Clark 8 , D. W. Cunningham 8 , A. M. Gabor 9 , R. Jonczyk 10 , S. Narayanan 8 , E. Sauar 11 and E. R. Weber 1 1 Department of Materials Science and Engineering, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA 2 RWE Schott Solar, 4 Suburban Park Drive, Billerica, MA 01821, USA; Presently at: JPK Consulting, 54 Northgate Road, Wellesley, MA 02481, USA 3 University of Konstanz, Department of Physics, 78457 Konstanz, Germany 4 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA 5 Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA 6 Pacific Northwest National Laboratory, Richland, WA 99352, USA 7 Formerly: National RenewableEnergy Laboratory, Golden, CO, USA/Presently: Siliconsultant, P.O. Box 1453, Evergreen, CO 80437, USA 8 BP Solar, 630 Solarex Court, Frederick, MD 21703, USA 9 Evergreen Solar, Inc., 259 Cedar Hill St., Marlboro, MA 01752, USA 10 GE Energy, 231 Lake Drive, Newark, DE 19702, USA 11 ScanWafer AS, PO Box 280, N-1323 Høvik, Norway We present a comprehensive summary of our observations of metal-rich particles in multicrystalline silicon (mc-Si) solar cell materials from multiple vendors, including directionally-solidified ingot-grown, sheet, and ribbon, as well as multicrystalline float zone materials contaminated during growth. In each material, the elemental nature, chemical states, and distributions of metal-rich particles are assessed by synchrotron-based analytical x-ray microprobe techniques. Certain universal physi- cal principles appear to govern the behavior of metals in nearly all materials: (a) Two types of metal-rich particles can be observed (metal silicide nanoprecipitates and metal-rich inclusions up to tens of microns in size, frequently oxidized), (b) spatial distributions of individual elements strongly depend on their solubility and diffusiv- ity, and (c) strong interactions exist between metals and certain types of structural defects. Differences in the distribution and elemental nature of metal contamination between different mc-Si materials can largely be explained by variations in crystal Received 29 August 2005 Copyright # 2006 John Wiley & Sons, Ltd. Revised 18 November 2005 * Correspondence to: Andrei Istratov, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Building 62-109 (MS 62R0203), Berkeley, CA 94720, USA. y E-mail: istratov@berkeley.edu Contract/grant sponsor: NREL; contract/grant number: AAT-2-31605-03. Contract/grant sponsor: U.S. Department of Energy; contract/grant number: DE-AC36-99GO10337. Contract/grant sponsor: Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences Division of the US Department of Energy; contract/grant number: DEAC03-76SF00098. Contract/grant sponsor: US Department of Energy, Office of Science, Office of Basic Energy Sciences; contract/grant number: W-31-109- ENG-38. Research