Optimization of [mu]c-Si1-x Gex :H Single-Junction Solar Cells with Enhanced Spectral Response and Improved Film Quality

• Published in: International journal of photoenergy 2015-01, Vol.2015
• Main Authors: Yen-Tang, Huang, Pei-Ling, Chen, Po-Wei, Chen, Hung-Jung, Hsu, Cheng-Hang, Hsu, Chuang-Chuang, Tsai
• Format: Article
• Language: English
• Subjects: Photovoltaic cells; Silicon wafers; Solar energy; Spectrum analysis
• ISSN: 1110-662X; 1687-529X
• DOI: 10.1155/2015/382814

Effects of RF power on optical, electrical, and structural properties of μc-Si1-x Gex :H films was reported. Raman and FTIR spectra from μc-Si1-x Gex :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-x Gex :H alloy. By decreasing RF power from 100 to 50 W at a fixed reactant gas ratio, the optical bandgap of μc-Si1-x Gex :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-x Gex :H film deposited at 60 W. By applying 0.9 μm thick μc-Si1-x Gex :H absorber with [subscript]XC[/subscript] 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-x Gex :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-x Gex :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%.