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Screen-Printed Al Back Contacts on Si Solar Cells: Issues and Some Solutions

Published online by Cambridge University Press:  31 January 2011

Vishal Mehta,
Bhushan Sopori,
Robert Reedy,
Bobby To,
Helio Moutinho and
Nuggehalli M. Ravindra
Vishal Mehta
Affiliation:
Vishal_mehta@nrel.gov, National Renewable Energy Laboratory, Golden, Colorado, United States
Bhushan Sopori
Affiliation:
Bhushan.Sopori@scholarone.net, National Renewable Energy Laboratory, Golden, Colorado, United States
Robert Reedy
Affiliation:
Bob.Reedy@nrel.gov, National Renewable Energy Laboratory, Golden, Colorado, United States
Bobby To
Affiliation:
Bobby.To@nrel.gov, National Renewable Energy Laboratory, Golden, Colorado, United States
Helio Moutinho
Affiliation:
helio.moutinho@nrel.gov, National Renewable Energy Laboratory, Golden, Colorado, United States
Nuggehalli M. Ravindra
Affiliation:
nmravindra@gmail.com, New Jersey Institute of Technology, Newark, New Jersey, United States
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Abstract

This paper identifies some mechanisms that lead to problems in back Al contact formation. Major issues are related to a basic problem that the Al melt has a large surface tension and tries to ball up during the firing step. Other issues arise from dissolution of the Si-Al interface and entrapment of glass within the Si-Al alloy. Si diffusion into Al can be applied to control the melt, while cooling rate can help improve the structure of various regions of the back contact for a favorable series resistance. We also discuss a modified time-temperature profile that can lead to a deep and uniform back-surface field.

Keywords

screen printingdiffusionalloy

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Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1210: Symposium Q – Photovoltaic Materials and Manufacturing Issues II , 2009, 1210-Q05-02
Copyright
Copyright © Materials Research Society 2010

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References

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