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High efficiency amorphous and nanocrystalline silicon based multi-junction solar cells deposited at high rates on textured Ag/ZnO back reflectors

Published online by Cambridge University Press:  31 January 2011

Guozhen Yue
Affiliation:
gyue@uni-solar.com, United Solar Ovonic LLC, 1100 West Maple Road, Troy, Michigan, 48084, United States, (248) 519-5317, (248) 362-4442
Laura Sivec
Affiliation:
lsivec@uni-solar.com, United Solar Ovonic LLC, Troy, Michigan, United States
Baojie Yan
Affiliation:
byan@uni-solar.com, United Solar Ovonic LLC, Troy, Michigan, United States
Jeff Yang
Affiliation:
jyang@uni-solar.com, United Solar Ovonic LLC, Troy, Michigan, United States
Subhendu Guha
Affiliation:
sguha@uni-solar.com, United Solar Ovonic LLC, Troy, Michigan, United States
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Abstract

We report our recent progress on nc-Si:H single-junction and a-Si:H/nc-Si:H/nc-Si:H triple-junction cells made by a modified very-high-frequency (MVHF) technique at deposition rates of 10-15 Å/s. First, we studied the effect of substrate texture on the nc-Si:H single-junction solar cell performance. We found that nc-Si:H single-junction cells made on bare stainless steel (SS) have a good fill factor (FF) of ˜0.73, while it decreased to ˜0.65 when the cells were deposited on textured Ag/ZnO back reflectors. The open-circuit voltage (Voc) also decreased. We used dark current-voltage (J-V), Raman, and X-ray diffraction (XRD) measurements to characterize the material properties. The dark J-V measurement showed that the reverse saturated current was increased by a factor of ˜30 when a textured Ag/ZnO back reflector was used. Raman results revealed that the nc-Si:H intrinsic layers in the two solar cells have similar crystallinity. However, they showed a different crystallographic orientation as indicated in XRD patterns. The material grown on Ag/ZnO has more random orientation than that on SS. These experimental results suggested that the deterioration of FF in nc-Si:H solar cells on textured Ag/ZnO was caused by poor nc-Si:H quality. Based on this study, we have improved our Ag/ZnO back reflector and the quality of nc-Si:H component cells and achieved an initial and stable active-area efficiencies of 13.4% and 12.1%, respectively, in an a-Si:H/nc-Si:H/nc-Si:H triple-junction cell.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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