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Triple Junction n-i-p Solar Cells with Hot-Wire Deposited Protocrystalline and Microcrystalline Silicon

Published online by Cambridge University Press:  01 February 2011

Ruud E.I. Schropp
Affiliation:
r.e.i.schropp@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands, +31-302533170, +31-302543165
Hongbo Li
Affiliation:
h.li@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands
Ronald H.J. Franken
Affiliation:
r.h.j.franken@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands
Jatindra K. Rath
Affiliation:
j.k.rath@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands
Karine van der Werf
Affiliation:
c.h.m.vanderwerf@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands
Jan Willem Schüttauf
Affiliation:
j.a.schuttauf@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands
Robert L. Stolk
Affiliation:
R.L.Stolk@phys.uu.nl, Utrecht University, Faculty of Science, Department of Physics and Astronomy,, SID - Physics of Devices,, P.O. Box 80.000, Utrecht, 3508 TA, Netherlands
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Abstract

We have implemented a number of methods to improve the performance of proto-Si/proto-SiGe/μc-Si:H triple junction n-i-p solar cells in which the top and bottom cell i-layers are deposited by Hot-Wire CVD. Firstly, a significant current enhancement is obtained by using textured Ag/ZnO back contacts developed in house instead of plain stainless steel. We studied the correlation between the integrated current density in the long wavelength range (650-1000 nm) with the back reflector surface roughness and clarified that the rms roughness from 2D AFM images correlates well with the long wavelength response of the cell when weighted with a Power Spectral Density function. For single junction 2-μm thick μc-Si:H n-i-p cells we improved the short circuit current density from the value of 15.2 mA/cm2 for plain stainless steel to 23.4 mA/cm2 for stainless steel coated with a textured Ag/ZnO back reflector.

Secondly, we optimized the μc-Si:H n-type doped layer on this rough back reflector, the n/i interface, and in addition used a profiling scheme for the H2/SiH4 ratio during i-layer deposition. The H2 dilution during growth was stepwise increased in order to prevent a transition to amorphous growth. The efficiency that was reached for a single junction μc-Si:H n-i-p cell was 8.5%, which is the highest reported value for hot-wire deposited cells of this kind, whereas the deposition rate of 2.1 Å/s is about twice as high as in record cells of this type so far. Moreover, these cells show to be totally stable under light-soaking tests.

Combining the above techniques, a rather thin triple junction cell (total silicon thickness 2.5 μm) has been obtained with an efficiency of 10.9%. Preliminary light-soaking tests show that this type of triple cells degrades by less than 4%.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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References

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