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CdSxTe1-x Alloying in CdS/CdTe Solar Cells

Published online by Cambridge University Press:  20 July 2011

Joel N. Duenow ,
Ramesh G. Dhere ,
Helio R. Moutinho ,
Bobby To ,
Joel W. Pankow ,
Darius Kuciauskas  and
Timothy A. Gessert
Joel N. Duenow
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
Ramesh G. Dhere
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
Helio R. Moutinho
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
Bobby To
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
Joel W. Pankow
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
Darius Kuciauskas
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
Timothy A. Gessert
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
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Abstract

A CdSxTe1-x layer forms by interdiffusion of CdS and CdTe during the fabrication of thinfilm CdTe photovoltaic (PV) devices. The CdSxTe1-x layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in this interdiffused CdSxTe1-x region. Further understanding, however, is essential to predict the role of this CdSxTe1-x layer in the operation of CdS/CdTe devices. In this study, CdSxTe1-x alloy films were deposited by radio-frequency magnetron sputtering and coevaporation from CdTe and CdS sources. Both radio-frequency-magnetron-sputtered and coevaporated CdSxTe1-x films of lower S content (x<0.3) have a cubic zincblende (ZB) structure akin to CdTe, whereas those of higher S content have a hexagonal wurtzite (WZ) structure like that of CdS. Films become less preferentially oriented as a result of a CdCl2 heat treatment at ∼400°C for 5 min. Films sputtered in a 1% O2/Ar ambient are amorphous as deposited, but show CdTe ZB, CdS WZ, and CdTe oxide phases after a CdCl2 heat treatment. Films sputtered in O2 partial pressure have a much wider bandgap than expected. This may be explained by nanocrystalline size effects seen previously [2] for sputtered oxygenated CdS (CdS:O) films.

Keywords

photovoltaicII-VIthin film
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1324: Symposium D – Compound Semiconductors for Energy Applications and Environmental Sustainability , 2011 , mrss11-1324-d14-03
Copyright
Copyright © Materials Research Society 2011

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References

REFERENCES

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