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Structural Properties of CdTe Thin Films for Solar Cell Applications Deposited on Flexible Foil Substrates

Published online by Cambridge University Press:  31 January 2011

Vasilios Palekis ,
Deidra Ranel Hodges ,
Don L Morel ,
Lee Stefanakos  and
Chris S Ferekides
Vasilios Palekis
Affiliation:
vpalekis@mail.usf.edu, University of South Florida, Electrical Engineering, Tampa, Florida, United States
Deidra Ranel Hodges
Affiliation:
dhodges@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, University of South Florida, Electrical Engineering, Tampa, Florida, United States
Chris S Ferekides
Affiliation:
ferekide@eng.usf.edu, United States
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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 and its high optical absorption coefficient. The typical CdTe thin film solar cell is of the superstrate configuration where a window layer (CdS), the absorber (CdTe), and a back contact are deposited onto a glass slide coated with a transparent electrode. Substrate CdTe solar cells where the above listed films are deposited in reverse order are not common. In this study, the growth of CdTe thin films deposited on foil substrates by the close-spaced sublimation (CSS) has been investigated for the purpose of fabricating substrate based CdTe solar cells. The CdTe films were deposited at substrate temperatures (TSUB) in the range of 300 to 600°C, and source temperatures (TSRC) in the 600 to 650°C range. The effect of the substrate-source temperature variations on the growth rate, film structure and morphology were studied using XRD and SEM. It was found that for low substrate temperature and as the growth rate increases, grain size was the same but the films appeared to be more uniform and more densely packed with less or no pinholes. The growth rate increased as the source temperature increased. The substrate temperature clearly influences the grain growth and the preferred orientation. As the substrate temperature increased the growth rate decreased and the grain size varied from 2 to 6 μm. XRD analysis showed that with the increase in substrate temperature film orientation changes from preferential along the (111) direction to a mix of (111) (220) and (311).

Keywords

II-VIphotovoltaiccrystal growth
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1165: Symposium M – Thin-Film Compound Semiconductor Photovoltaics–2009 , 2009 , 1165-M08-26
Copyright
Copyright © Materials Research Society 2009

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