Abstract
As the demand for high-quality solar-cell feedstock exceeds supply and drives prices upwards, cheaper but dirtier alternative feedstock materials are being developed1,2,3. Successful use of these alternative feedstocks requires that one rigorously control the deleterious effects of the more abundant metallic impurities. In this study, we demonstrate how metal nanodefect engineering can be used to reduce the electrical activity of metallic impurities, resulting in dramatic enhancements of performance even in heavily contaminated solar-cell material. Highly sensitive synchrotron-based measurements4,5 directly confirm that the spatial and size distributions of metal nanodefects regulate the minority-carrier diffusion length, a key parameter for determining the actual performance of solar-cell devices. By engineering the distributions of metal-impurity nanodefects in a controlled fashion, the minority-carrier diffusion length can be increased by up to a factor of four, indicating that the use of lower-quality feedstocks with proper controls may be a viable alternative to producing cost-effective solar cells.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Rent or buy this article
Prices vary by article type
from$1.95
to$39.95
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Woditsch, P. & Koch, W. Solar grade silicon feedstock supply for PV industry. Solar Energy Mater. Solar Cells 72, 11–26 (2002).
Yuge, N. et al. Purification of metallurgical-grade silicon up to solar grade. Prog. Photovolt. Res. Appl. 9, 203–209 (2001).
Khattak, C. P., Joyce, D. B. & Schmid, F. A simple process to remove boron from metallurgical grade silicon. Solar Energy Mater. Solar Cells 74, 77–89 (2002).
Yun, W. et al. Nanometer focusing of hard X-rays by phase zone plates. Rev. Sci. Instrum. 70, 2238–2241 (1999).
Cai, Z. et al. Performance of a high-resolution X-ray microprobe at the advanced photon source. AIP Conf. Proc. 521, 31–34 (2000).
Davis, J. R. et al. Impurities in silicon solar cells. IEEE Trans. Electron Dev. 27, 677–687 (1980).
Pizzini, S., Bigoni, L., Beghi, M. & Chemelli, C. On the effect of impurities on the photovoltaic behavior of solar grade silicon. II. Influence of titanium, vanadium, chromium, iron, and zirconium on photovoltaic behavior of polycrystalline solar cells. J. Electrochem. Soc. 133, 2363–2373 (1986).
Istratov, A. A., Hieslmair, H. & Weber, E. R. Iron contamination in silicon technology. Appl. Phys. A 70, 489–534 (2000).
Kittler, M. & Seifert, W. Estimation of the upper limit of the minority-carrier diffusion length in multicrystalline silicon: Limitation of the action of gettering an passivation of dislocations. Solid State Phenom. 95–96, 197–204 (2004).
Plekhanov, P. S., Gafiteanu, R., Gosele, U. M. & Tan, T. Y. Modeling of gettering of precipitated impurities from Si for carrier lifetime improvement in solar cell applications. J. Appl. Phys. 86, 2453–2458 (1999).
Myers, S. M., Seibt, M. & Schröter, W. Mechanisms of transition metal gettering in silicon. J. Appl. Phys. 88, 3795–3819 (2000).
Dorward, R. C. & Kirkaldy, J. S. Effect of grain-boundaries on the solubility of copper in silicon. J. Mater. Sci. 3, 502–506 (1968).
Istratov, A. A., Huber, W. & Weber, E. R. Experimental evidence for the presence of segregation and relaxation gettering of iron in polysilicon layers. Appl. Phys. Lett. 85, 4472–4474 (2004).
Green, M. A., Emery, K., King, D. L., Igari, S. & Warta, W. Solar cell efficiency tables (version 24). Prog. Photovolt. Res. Appl. 12, 365–372 (2004).
Macdonald, D., Cuevas, A., Kinomura, A. & Nakano, Y. in Proc. 29th IEEE Photovoltaics Specialist Conf. 285 (IEEE, Piscataway, New Jersey, 2002).
McHugo, S. A. et al. Synchrotron-based impurity mapping. J. Cryst. Growth 210, 395–400 (2000).
Manceau, A., Marcus, M. A. & Tamura, N. in Applications of Synchrotron Radiation in Low-temperature Geochemistry and Environmental Science Vol. 49 (ed. Sturchio, N. C.) 341–428 (Mineralogical Society of America, Washington DC, 2002).
Buonassisi, T. et al. Quantifying the effect of metal-rich precipitates on minority carrier diffusion length in multicrystalline silicon using synchrotron-based spectrally-resolved X-ray beam induced current. Appl. Phys. Lett. 87, 044101 (2005).
Schönecker, A., Geerligs, L. J. & Müller, A. Casting technologies for solar silicon wafers: block casting and ribbon-growth-on-substrate. Solid State Phenom. 95–96, 149–158 (2003).
Hall, R. B. et al. Columnar grained polycrystalline solar cell substrate and improved method of manufacture. US Patent 6,111,191 (2000).
Hiraga, T., Anderson, I. M. & Kohlstedt, D. L. Grain boundaries as reservoirs of incompatible elements in the Earth’s mantle. Nature 427, 699–703 (2004).
Blavette, D., Cadel, E., Fraczkiewicz, A. & Menand, A. Three-dimensional atomic-scale imaging of impurity segregation to line defects. Science 286, 2317–2319 (1999).
Ziegler, A. et al. Interface structure and atomic bonding characteristics in silicon nitride ceramics. Science 306, 1768–1770 (2004).
Seager, C. H. Grain boundaries in polycrystalline silicon. Annu. Rev. Mater. Sci. 15, 271–302 (1985).
Buonassisi, T. et al. Analysis of copper-rich precipitates in silicon: chemical state, gettering, and impact on multicrystalline silicon solar cell material. J. Appl. Phys. 97, 063503 (2005).
Macdonald, D. H., Geerligs, L. J. & Azzizi, A. Iron detection in crystalline silicon by carrier lifetime measurements for arbitrary injection and doping. J. Appl. Phys. 95, 1021–1028 (2004).
Lu, J., Wagener, M., Rozgonyi, G., Rand, J. & Jonczyk, R. Effects of grain boundary on impurity gettering and oxygen precipitation in polycrystalline sheet silicon. J. Appl. Phys. 94, 140–144 (2003).
Acknowledgements
Collaboration with M. Heuer, S. Fakra, M. D. Pickett, R. Jonczyk, T. F. Ciszek, K. O. Dijon, J. Isenberg, W. Warta, R. Schindler and G. Willeke is gratefully appreciated. This work was funded by National Renewable Energy Laboratory subcontract AAT-2-31605-03. Use of the Advanced Photon Source and of the Advanced Light Source is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract Numbers W-31-109-ENG-38 and DEAC03-76SF00098, respectively.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Supplementary Information
Supporting supplementary material (PDF 61 kb)
Rights and permissions
About this article
Cite this article
Buonassisi, T., Istratov, A., Marcus, M. et al. Engineering metal-impurity nanodefects for low-cost solar cells. Nature Mater 4, 676–679 (2005). https://doi.org/10.1038/nmat1457
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nmat1457
This article is cited by
-
Effect of Cooling Rate during Thermal Processes on the Electrical Properties of Cast Multi-Crystalline Silicon
Silicon (2022)
-
Finite Element Analysis and Techno-economic Modeling of Solar Silicon Molten Salt Electrolysis
JOM (2021)
-
Point defect engineering in thin-film solar cells
Nature Reviews Materials (2018)
-
Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology
Scientific Reports (2015)
-
Pathways to Solar Grade Silicon
Silicon (2015)