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Improved Ambipolar Diffusion Length in a-Si1-xGex:H Alloys for Multi-Junction Solar Cells

Published online by Cambridge University Press:  15 February 2011

J. Fölsch ,
F. Finger ,
T. Kulessa ,
F. Siebke ,
W. Beyer  and
H. Wagner
J. Fölsch
Affiliation:
Institut für Schicht- und Ionentechnik, Forschungszentrum Jölich, D-52425 Jölich, Germany
F. Finger
Affiliation:
Institut für Schicht- und Ionentechnik, Forschungszentrum Jölich, D-52425 Jölich, Germany
T. Kulessa
Affiliation:
Institut für Schicht- und Ionentechnik, Forschungszentrum Jölich, D-52425 Jölich, Germany
F. Siebke
Affiliation:
Institut für Schicht- und Ionentechnik, Forschungszentrum Jölich, D-52425 Jölich, Germany
W. Beyer
Affiliation:
Institut für Schicht- und Ionentechnik, Forschungszentrum Jölich, D-52425 Jölich, Germany
H. Wagner
Affiliation:
Institut für Schicht- und Ionentechnik, Forschungszentrum Jölich, D-52425 Jölich, Germany
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Abstract

To prepare hydrogenated amorphous silicon-germanium alloys as low gap material for multi-junction solar cells in plasma enhanced chemical vapour deposition, the well established concept of strong dilution of the process gases with hydrogen has been used. Two different regimes of alloying were found: for low Ge content (x < 0.40) we observe material with low defect density, small Urbach energy and high values of the ambipolar diffusion length. In the regime of high Ge content (x > 0.40) the defect densities and Urbach energies are high and the values of the ambipolar diffusion length low. The transition is accompanied by the appearance of a low-temperature peak in hydrogen effusion experiments indicating a void rich film structure. Material from just above and below the transition zone is used in pin solar cells leading to a much enhanced red response compared with a-Si:H cells. The differences seen in the material quality are mirrored in the solar cell properties. By carefully adjusting the active layer thickness material with low diffusion length shows also reasonable solar cell performance.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 377: Symposium A – Amorphous Silicon Technology 1995 , 1995 , 517
Copyright
Copyright © Materials Research Society 1995

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References

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