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Impact of Impurities on the Mechanical Strength of Multicrystalline Silicon

: Orellana Perez, T.; Funke, C.; Fütterer, W.; Riepe, S.; Möller, H.J.; Tejado Garrido, E.M.; Pastor Caño, J.Y.

Volltext urn:nbn:de:0011-n-2210386 (634 KByte PDF)
MD5 Fingerprint: 907ceaae9a925df4d7ff8f3837c99c76
Erstellt am: 7.12.2012

European Commission:
26th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC. Proceedings : 5th to 9th September 2011 at the CCH - Congress Centre and International Fair Hamburg in Germany
München: WIP-Renewable Energies, 2011
ISBN: 3-936338-27-2
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <26, 2011, Hamburg>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()
Materialien - Solarzellen und Technologie; Silicium-Photovoltaik; Silicium-Photovoltaik; Feedstock; Kristallisation und Wafering; Charakterisierung von Prozess- und Silicium-Materialien; Feedstock; Kristallisation und Wafering

The usage of more inexpensive silicon feedstock for crystallizing mc-Si blocks promises cost reduction for the photovoltaic market. For example, less expensive substrates of upgraded metallurgical silicon (UMG-Si) are used as a mechanical support for the epitaxial solar cell. This feedstock has higher content of impurities which influences cell performance and mechanical strength of the wafers. Thus, it is of importance to know these effects in order to know which impurities should be preferentially removed or prevented during the crystallization process. Metals like aluminum (Al) can decrease the mechanical strength due to micro-cracking of the silicon matrix and introduction of high values of thermal residual stress. Additionally, silicon oxide (SiOx) lowers the mechanical strength of mc-Si due to thermal residual stresses and stress intensification when an external load is applied in the surrounding of the particle. Silicon carbide (SiC) introduces thermal residual stresses and intensifies slightly the stress in the surrounding of the particle but can have a toughening effect on the silicon matrix. Finally, silicon nitride (Si3N4) does not influence significantly the mechanical strength of mc- Si and can have a toughening effect on the silicon matrix.