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Understanding the Properties of Silicon Solar Cells Aluminium Contact Layers and Its Effect on Mechanical Stability

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DOI: 10.4236/msa.2013.42013    5,118 Downloads   9,260 Views   Citations

ABSTRACT

As the thickness of silicon solar wafer and solar cells becomes thinner, the cells are subjected to high stress due to the thermal coefficient mismatch induced by metallization process. Handling and bowing problems associated with thinner wafers become increasingly important, as these can lead to cells cracking and thus to high yield losses. The goal of this work to provide experimental understanding of Al rear side microstructure development and mechanical properties as well as correlate the obtained results with fracture behaviour of the cell. It is shown that the aluminium back contact has a complex microstructure, consisting of five main components: 1) the back surface field layer; 2) a eutectic layer; 3) spherical (3 - 5 μm) hypereutectic Al-Si particles surrounded by a thin aluminium oxide layer (200 nm); 4) a bis- muth-silicate glass matrix; and 5) pores (14 vol%). It was concluded that the eutectic layer thickness and waviness depends on Al particle size, amount of Al paste and textured surface roughness of silicon wafers. The Young’s modulus of the Al-Si particles is estimated by nano-indentation and the overall Young’s modulus is estimated on the basis of bowing measurements and found to be ~43 GPa. It was found, that there is a relation between aluminium paste composition, eutectic layer thickness, mechanical strength and bowing of solar cells. Three main parameters were found to affect the mechanical strength of mc-silicon solar cells with an aluminium contact layer, namely the eutectic layer thickness and uniformity, the Al layer thickness (which results from the Al particle size and its distribution), and the amount of porosity and the bismuth glass fraction.

Conflicts of Interest

The authors declare no conflicts of interest.

Cite this paper

V. Popovich, M. Maris, M. Janssen, I. Bennett and I. Richardson, "Understanding the Properties of Silicon Solar Cells Aluminium Contact Layers and Its Effect on Mechanical Stability," Materials Sciences and Applications, Vol. 4 No. 2, 2013, pp. 118-127. doi: 10.4236/msa.2013.42013.

References

[1] T. van Amstel, V. A. Popovich, P. C. de Jong and I. G. Romijn, “Modeling Mechanical Aspects of the Aspire Cell,” Proceedings of the 23rd European Photovoltaic Solar Energy Conference, Valencia, 2008.
[2] F. Huster, “Investigation of the Alloying Process of Screen Printing Aluminum Pastes for the BSF Formation on Silicon Solar Cells,” 20th European Photovoltaic Solar Energy Conference, Barcelona, 2005.
[3] F. Huster, “Aluminum-Back Surface Field: Bow Investigation and Elimination,” 20th European Photovoltaic Solar Energy Conference and Exhibition, Barcelona, 2005, pp. 635-638.
[4] S. Kim, “Aluminum Paste (Lead-Free/Low Bow) for Thin Wafers,” IEEE 31st Photovoltaic Specialists Conference and Exhibition, Orlando, 2004.
[5] J. T. Armstrong, “Quantitative Elemental Analysis of In dividual Microparticles with Electron Beam Instruments.” In: K. F. J. Heinrich and D. E. Newbury, Eds., Electron Probe Quantitation, Plenum Press, New York, 1991, pp. 261-315.
[6] http://icsdweb.fiz-karlsruhe.de/index.php
[7] W. C. Oliver and G. M. Pharr, “An Improved Technique for Determining Hardness and Elastic Modulus Using Load and Displacement Sensing Indentation Experiments,” Journal of Materials Research, Vol. 7, No. 6, 1992, pp. 1564-1583. doi:10.1557/JMR.1992.1564
[8] ASTM C1161-02c, Standard Test Method for Flexural Strength of Advance Ceramics at Ambient Temperature, 2008.
[9] ASTM C1341-06, Standard Test Method for Flexural Properties of Continuous Fiber-Reinforces Advance Ceramic Composites, Current Edition, 2006.
[10] J. M. Gere and B. J. Goodno, “Mechanics of Materials,” Seventh Edition, Cengange Learning, 2009.
[11] M. Trunov, et al., “Effect of Polymorphic Phase Transformations in Al2O3 Film on Oxidation Kinetics of Aluminum Powders,” Combustion and Flame, Vol. 140, No. 4, 2006, pp. 310-318. doi:10.1016/j.combustflame.2004.10.010
[12] Z. Peng, J. Gong and H. Miao, “On the Description of Indentation Size Effect in Hardness Testing for Ceramics: Analysis of the Nano-Indentation Data,” Journal of the European Ceramic Society, Vol. 24, No. 8, 2004, pp. 2193-2201. doi:10.1016/S0955-2219(03)00641-1
[13] M. Warmuzek, “Aluminum-Silicon Casting Alloys: Atlas of Micrographs,” ASM International, 2004.
[14] T. van Amstel, V. A. Popovich, P. C. de Jong and I. J. Bennett, “A Multiscale Model of the Aluminium Layer at the Rear Side of a Solar Cell,” Proceedings of the 24th European Photovoltaic Solar Energy Conference, Hamburg, 2009.

  
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