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Use of HCL gas gettering in the epitaxial wafer equivalent concept

: Hampel, J.; Boldt, F.M.; Wiehl, N.; Hampel, G.; Kratz, J.V.; Reber, S.

Volltext urn:nbn:de:0011-n-1563907 (135 KByte PDF)
MD5 Fingerprint: fa400db40f9cd257ed505adfaeb63986
Erstellt am: 11.8.2012

European Commission:
25th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2010. Proceedings : 5th World Conference on Photovoltaic Energy Conversion, 6-10 , September 2010, Valencia, Spain
München: WIP-Renewable Energies, 2010
ISBN: 3-936338-26-4
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <25, 2010, Valencia>
World Conference on Photovoltaic Energy Conversion <5, 2010, Valencia>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()

The concept of the epitaxial wafer equivalent (EpiWE) is pursued at the Fraunhofer ISE as an option to reduce the cost of silicon solar cells. Within this concept, only a small amount of the expensive high purity silicon is needed for the epitaxial deposition on a low-cost substrate made from low-quality silicon. A challenging task is the control of the impurity contents in the low-grade silicon substrate. Especially transition metals like Fe, Mn, and Cr act as recombination centres and degrade the minority carrier lifetime once they diffuse into the active layer. Gettering with HCl gas is an effective and fast method to reduce the metals mentioned above to an appropriate level and can be performed prior to the epitaxial deposition. This paper presents a reduction of metal impurity concentrations up to two orders of magnitude obtained by HCl gettering of metallurgical grade (MG) and upgraded metallurgical grade (UMG) silicon. Additionally, solar cell results are shown, demonstrating the improvement of EpiWE solar cells by HCl gas gettering.