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International Journal of Photoenergy
Volume 2015, Article ID 382814, 9 pages
http://dx.doi.org/10.1155/2015/382814
Research Article

Optimization of μc-Si1−xGex:H Single-Junction Solar Cells with Enhanced Spectral Response and Improved Film Quality

Department of Photonics, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan

Received 3 April 2015; Accepted 15 June 2015

Academic Editor: Jürgen Hüpkes

Copyright © 2015 Yen-Tang Huang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Effects of RF power on optical, electrical, and structural properties of μc-Si1−xGex:H films was reported. Raman and FTIR spectra from μc-Si1−xGex:H films reflected the variation in microstructure and bonding configuration. Unlike increasing the germane concentration for Ge incorporation, low RF power enhanced Ge incorporation efficiency in μc-Si1−xGex:H alloy. By decreasing RF power from 100 to 50 W at a fixed reactant gas ratio, the optical bandgap of μc-Si1−xGex:H was reduced owing to the increase in Ge content from 11.2 to 23.8 at.%, while Ge-related defects and amorphous phase were increased. Consequently, photo conductivity of 1.62 × 10−5 S/cm was obtained for the μc-Si1−xGex:H film deposited at 60 W. By applying 0.9 μm thick μc-Si1−xGex:H absorber with of 48% and [Ge] of 16.4 at.% in the single-junction cell, efficiency of 6.18% was obtained. The long-wavelength response of μc-Si1−xGex:H cell was significantly enhanced compared with the μc-Si:H cell. In the case of tandem cells, 0.24 μm a-Si:H/0.9 μm μc-Si1−xGex:H tandem cell exhibited a comparable spectral response as 0.24 μm a-Si:H/1.4 μm μc-Si:H tandem cell and achieved an efficiency of 9.44%.