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Simulation of Symmetrically Doped Silicon Nanowire Solar Cells

Published online by Cambridge University Press:  22 August 2011

Felix Voigt ,
Thomas Stelzner  and
Silke H. Christiansen
Felix Voigt
Affiliation:
Institute of Photonic Technology, Jena, Germany. Institute of Physics, University of Oldenburg, Germany.
Thomas Stelzner
Affiliation:
Institute of Photonic Technology, Jena, Germany.
Silke H. Christiansen
Affiliation:
Institute of Photonic Technology, Jena, Germany. Max Planck Institute for the Science of Light, Erlangen, Germany.
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Abstract

Silicon nanowire solar cells were simulated using the Silvaco TCAD software kit. For optimization of speed the simulations were performed in cylinder coordinates with cylindrical symmetry. Symmetric doping was assumed with a dopant density of 1018 cm-3 in the p-type core and inside the n-type shell. In the implementation a cathode contact was wrapped around the semiconductor nanorod and an anode was assumed at the bottom of the rod. Optimization of cell efficiency was performed with regard to the rod radius and the rod length. In both optimization processes clear maxima in efficiency were visible, resulting in an optimal radius of 66 nm with the pn junction at 43.5 nm and an optimal rod length of about 48 μm. The maximum of efficiency with respect to the rod radius is due to a decrease of short-circuit current density (Jsc) and an increase of open-circuit voltage (Uoc) with radius, while the maximum with respect to the rod length is explained by the combination of an increase of Jsc and a decrease of Uoc. Fill factors stay rather constant at values between 0.6 and 0.8. Further, the influence of a back surface field (BSF) layer was surveyed in simulations. Positioning the BSF next to the cathode contact considerably improved cell efficiency. In addition, simulations with a cathode contact on top of the nanowire structure were undertaken. No severe deterioration of cell performance with increasing radius was observed so far in this configuration. Hence, nanorods with much larger radii can be used for solar cells using this contact scheme. In comparison to simulations with wrapped cathode contacts, Jsc and Uoc and therefore efficiency is considerably improved.

Keywords

simulationphotovoltaicnanostructure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1322: Symposium B – Third-Generation and Emerging Solar-Cell Technologies , 2011 , mrss11-1322-b08-66
Copyright
Copyright © Materials Research Society 2011

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References

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