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Mechanical Properties and Adhesion of CdTe/CdS Thin Film Solar Cells Deposited on Flexible Foil Substrates

Published online by Cambridge University Press:  31 January 2011

Deidra Ranel Hodges ,
Vasilios Palekis ,
Shweta Bhandaru ,
Kartikay Singh ,
Don L Morel  and
Lee Stefanakos
Deidra Ranel Hodges
Affiliation:
dhodges@mail.usf.edu, University of South Florida, Electrical Engineering, 4202 E. Fowler Ave., ENB118, Tampa, Florida, 33620, United States, 813-974-3209
Vasilios Palekis
Affiliation:
vpalekis@mail.usf.edu, University Of South Florida, Electrical Engineering, Tampa, Florida, United States
Shweta Bhandaru
Affiliation:
sbhandaru@mail.usf.edu, University Of South Florida, Electrical Engineering, Tampa, Florida, United States
Kartikay Singh
Affiliation:
KSingh@mail.usf.edu, University Of South Florida, Electrical Engineering, Tampa, Florida, United States
Don L Morel
Affiliation:
morel@eng.usf.edu, United States
Lee Stefanakos
Affiliation:
stefanak@eng.usf.edu, United States Minor Outlying Islands
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Abstract

Cadmium telluride (CdTe) is a leading thin film photovoltaic (PV) material due to its near ideal band gap of 1.45 eV, its high optical absorption coefficient and availability of various device fabrication methods. Superstrate CdTe solar cells fabricated on glass have to-date exhibited efficiencies of 16.5%. Work on substrate devices has been limited due to difficulties associated with the formation of an ohmic contact with CdTe. Foil substrate curvature, flaking, delamination and adhesion as a result of compressive strain due to the coefficient of thermal expansion (CTE) mismatch between the flexible foil substrate and the solar cell films has been studied. Thin films have been characterized by AFM, XRD, SEM, ASTM D3359-08 tape test, and solar cells have been characterized using J-V and spectral measurements. Adhesion improves by minimizing the mismatch of the CTE . A CdCl2 treatment is important for high efficiency solar cells. The treatment influences the microstructure and interface properties of the layers. The effect of the current CdCl2 chemical treatment increases flaking and has to be optimized for the CdTe substrate cell on foil. We have also fabricated solar cells on tantalum, molybdenum and tungsten foils, all with lower CTEs than SS430. We are currently producing solar cells with a VOC of 630mV, a 50% fill factor and over 6.0% efficiency.

Keywords

photovoltaicadhesionthin film
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1165: Symposium M – Thin-Film Compound Semiconductor Photovoltaics–2009 , 2009 , 1165-M02-09
Copyright
Copyright © Materials Research Society 2009

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