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Effect of Bandgap Grading on the Performance of a-Si1-xGex:H Single-Junction Thin-Film Solar Cells

Published online by Cambridge University Press:  23 June 2011

H. J. Hsu ,
C. M. Wang ,
C. H. Hsu  and
C. C. Tsai
H. J. Hsu
Affiliation:
Department of Photonics, National Chiao Tung University, Hsinchu, Taiwan
C. M. Wang
Affiliation:
Department of Photonics, National Chiao Tung University, Hsinchu, Taiwan
C. H. Hsu
Affiliation:
Department of Photonics, National Chiao Tung University, Hsinchu, Taiwan
C. C. Tsai
Affiliation:
Department of Photonics, National Chiao Tung University, Hsinchu, Taiwan
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Abstract

In this work, the effect of bandgap grading of hydrogenated amorphous silicon germanium (a-Si1-xGex:H) absorber near the p/i and the i/n interfaces was investigated. The a-Si1-xGex:H single-junction solar cells were improved by applying both p/i grading and i/n grading. Our results showed that both the p/i and the i/n grading can increase the open-circuit voltage (VOC) as compared to the cell without grading. The i/n grading can further improve the FF. Presumably the potential gradient created by the i/n grading can facilitate the hole transport thus it can improve the FF. However, the JSC decreased as the i/n grading width increased. The reduction of JSC was due to the loss in the red response, which can be attributed to the replacement of lower bandgap material by the larger ones. Combining the effects of VOC, JSC and FF, a suitable thickness of the p/i and the i/n grading was 20 nm and 45 nm, respectively. Finally, the grading structures accompanied with further optimization of doped layers were integrated to achieve a cell efficiency of 8.59 %.

Keywords

amorphousphotovoltaicplasma-enhanced CVD (PECVD) (chemical reaction)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1321: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology , 2011 , mrss11-1321-a01-05
Copyright
Copyright © Materials Research Society 2011

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References

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