Title:	World Class Solar Cell Efficiency on n-Type Cz UMG Silicon Wafers by Heterojunction Technology
Author(s):	J. Kraiem, P. Papet, J. Degoulange, M. Forster, O. Nichiporuk, D. Grosset-Bourbange, F. Cocco, R. Einhaus
Keywords:	Heterojunction, n-Type, UMG Silicon
Topic:	Wafer-Based Silicon Solar Cells and Materials Technology
Subtopic:	Silicon Solar Cell Improvements
Event:	27th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2BO.6.6
Pages:	657 - 660
ISBN:	3-936338-28-0
Paper DOI:	10.4229/27thEUPVSEC2012-2BO.6.6
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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Highly purified n-type UMG (“Upgraded Metallurgical”) Silicon shows a strong potential for high efficiency low cost solar cells. Compared to p-type Silicon, n-type Silicon is in general less susceptible to lifetime degradation due to residual metal impurities or to light induced degradation due to the Boron-Oxygen complex. In this work a 15kg 6 inch mono-c Cz Silicon ingot has been grown from 100% highly purified UMG Silicon obtained with the PHOTOSIL process. In this feedstock the Boron and Phosphorus concentrations measured by GDMS were found to be 0.3 ppmw and 2 ppmw respectively. The resulting ingot is n-type, fully mono-crystalline and has a resistivity from 0.2 to 1 ohm.cm. Other impurities, especially metals were not detectable with the analysis techniques applied (GDMS, ICP OES). The ingot was cut into 125x125 mm2 pseudo square wafers of 180 micron thickness. A first series of solar cells were processed on these wafers using an industrial hetero-junction process of Roth & Rau. The best solar cell had an energy conversion efficiency of 19.0% (average: 18.6%) under standard testing conditions with a very high Voc of 725mV. According to the knowledge of authors this is the highest efficiency ever reported on industrial type solar cells fabricated on 100% UMG Silicon.