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The Problem of the Top Cell for the Micromorph Tandem

Published online by Cambridge University Press:  15 February 2011

Rainer Platz ,
J. Meier ,
D. Fischer ,
S. Dubail  and
A. Shah
Rainer Platz
Affiliation:
Institut de Microtechnique, Université de Neuchâtel, Rue, A.-L.Breguet 2, CH-2000 Neuchâtel, Switzerland, platz@imt.unine.ch;http://www-nucromorph.unine.ch
J. Meier
Affiliation:
Institut de Microtechnique, Université de Neuchâtel, Rue, A.-L.Breguet 2, CH-2000 Neuchâtel, Switzerland, platz@imt.unine.ch;http://www-nucromorph.unine.ch
D. Fischer
Affiliation:
Institut de Microtechnique, Université de Neuchâtel, Rue, A.-L.Breguet 2, CH-2000 Neuchâtel, Switzerland, platz@imt.unine.ch;http://www-nucromorph.unine.ch
S. Dubail
Affiliation:
Institut de Microtechnique, Université de Neuchâtel, Rue, A.-L.Breguet 2, CH-2000 Neuchâtel, Switzerland, platz@imt.unine.ch;http://www-nucromorph.unine.ch
A. Shah
Affiliation:
Institut de Microtechnique, Université de Neuchâtel, Rue, A.-L.Breguet 2, CH-2000 Neuchâtel, Switzerland, platz@imt.unine.ch;http://www-nucromorph.unine.ch
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Abstract

A detailed study of the influence of different materials for the amorphous top cell on the stabilized efficiency of amorphous silicon/microcrystalline silicon (”micromorph”) tandem cells is presented. The authors investigate different amorphous i-layer materials which are applied in cells with varying thicknesses. It is shown that it is preferable to optimize the top cell in order to obtain a high current rather than a high voltage.

A simple optical and electrical model is presented which allows one to predict the optimum optical bandgap of the i-layer material of the top cell and to determine its optimum thickness for maximum stabilized efficiency. By means of this model it is shown that the optimum top cell for a total cell current of 26 mA/cm2 should contain an about 2500 Å thick i-layer with an optical gap Eo4 ≃ 1.8 eV. The model furthermore shows that it is desirable to obtain slightly bottom-limited conditions after degradation in order to maximize the output power.

A stabilized efficiency of 10.7 % for a micromorph tandem cell has been confirmed by an independent measurement (FhG-ISE). Another such cell yields a stabilized efficiency of 11.2 % as measured in our laboratory.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 467: Symposium A – Amorphous and Microcrystalline Silicon Technology - 1997 , 1997 , 699
Copyright
Copyright © Materials Research Society 1997

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References

REFERENCES

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