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High Efficiency Sputtered CdS/CdTe Cells without CdCl2 Activation

Published online by Cambridge University Press:  20 June 2011

N.R. Paudel ,
K.A. Wieland  and
A.D. Compaan
N.R. Paudel
Affiliation:
Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 USA
K.A. Wieland
Affiliation:
Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 USA
A.D. Compaan
Affiliation:
Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 USA
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Abstract

Polycrystalline thin-film CdS/CdTe PV cells nearly always require “activation” with vapors containing chlorine and oxygen near 400 oC in order to realize the highest cell performance, even when growth occurs near 600 oC. In this study we have used film growth near 270 oC by magnetron sputtering in an oxygen-free ambient and have studied the effects of post-deposition heat treatments for 20 minutes at 400, 425 and 450 oC without CdCl2 in a dry air ambient. The heat treatments enhanced grain growth and produced re-crystallization of the CdTe film at all three temperatures, but 450 oC was required to reach the best electrical performance. Grain size increased from a couple of hundred nanometers to more than a micron as the preferred (111) growth orientation decreased. Efficiencies up to 11.6% were achieved with no CdCl2 compared to ~13% with activation at 387 oC in the presence of CdCl2 vapors. X-ray diffraction and quantum efficiency measurements show interdiffusion of CdS and CdTe at 450 oC comparable with a standard CdCl2 treatment at 387 oC. The results are discussed in terms of CdSTe alloy gradients and minority-carrier diffusion lengths.

Keywords

thin filmsputteringcrystal growth
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1323: Symposium C – Advanced Materials Processing for Scalable Solar-Cell Manufacturing , 2011 , mrss11-1323-c06-03
Copyright
Copyright © Materials Research Society 2011

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References

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