Fabrication and characterization of 18.6% efficient multicrystalline silicon solar cells
- Georgia Inst. of Tech., Atlanta, GA (United States). Univ. Center of Excellence for Photovoltaics Research and Education
Solar cell efficiencies as high as 18.6% (1 cm{sup 2} area) have been achieved by a process which involves impurity gettering and effective back surface recombination velocity reduction of 0.65 {Omega}-cm multicrystalline silicon (mc-Si) grown by the heat exchanger method (HEM). Contactless photoconductance decay (PCD) analysis revealed that the bulk lifetime ({tau}{sub b}) in HEM samples after phosphorus gettering can exceed 100 {micro}s. At these {tau}{sub b} levels, the back surface recombination velocity (S{sub b}) resulting from unoptimized back surface field (BSF), S{sub b} values in this study were lowered from 8,000--10,000 cm/s range to 2,000 cm/s for HEM mc-Si devices. This combination of high {tau}{sub b} and moderately low S{sub b} resulted in the 18.6% device efficiency. Detailed model calculations indicate that lowering S{sub b} further can raise the efficiency of similar HEM mc-Si devices above 19.0%, thus closing the efficiency gap between good quality, untextured single crystal and mc-Si solar cells. For less efficient devices formed on the same material, the presence of electrically active extended defects have been found to be the main cause for the performance degradation. A combination of light beam induced current (LBIC) scans as well as forward-biased current measurements have been used to analyze the effects of these extended defects on cell performance.
- OSTI ID:
- 638407
- Journal Information:
- IEEE Transactions on Electron Devices, Journal Name: IEEE Transactions on Electron Devices Journal Issue: 8 Vol. 45; ISSN 0018-9383; ISSN IETDAI
- Country of Publication:
- United States
- Language:
- English
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