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Doped Self-Aligned Metallization for Solar Cells

Published online by Cambridge University Press:  03 March 2011

Ernest A. Addo
Affiliation:
Department of Material Science and Engineering, University of Delaware, Newark, Delaware 19716, and AstroPower Inc., Newark, Delaware 19716
S. Ismat Shah
Affiliation:
Department of Physics and Astronomy and Department of Material Science and Engineering, University of Delaware, Newark, Delaware 19716
Robert Opila
Affiliation:
Department of Material Science and Engineering, University of Delaware, Newark, Delaware 19716
Allen M. Barnett
Affiliation:
AstroPower Inc., Newark, Delaware 19716
Kevin Allison
Affiliation:
AstroPower Inc., Newark, Delaware 19716
Oleg Sulima
Affiliation:
AstroPower Inc., Newark, Delaware 19716
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Abstract

Metal contacts using doped self-aligning metallization to [100] and [111] p-type silicon were investigated. Contacts formed in this manner allow the formation of a pn-junction and provide front metallization for photovoltaic applications. Formulated screen-printable thick films were annealed above Ag/Si eutectic temperature of 830 °C. The annealing process resulted in a junction depth of 0.3–1.1 μm with improved Ag/Si metal contacts due to the reduction of parasitic native oxide layer via the use of a wetting agent. The technique inhibits shunts (high conductivity paths through the solar cell pn-junction caused by excessive metal penetration) due to limited solubility of Ag in Si. The technique also reduces series resistance (a parasitic resistance due to surface states that also limit solar cell performance) due to a robust thermal processing window. The use of magnesium (Mg) as a wetting agent in the thick film Ag matrix was explored. We observed a correlation between increased wetting and improved dark saturation current J02 in the absence of a pre-existing junction.

Type
Articles
Copyright
Copyright © Materials Research Society 2004

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References

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