Resistivity topography: a grain boundary characterisation method

Solar cells made from multicrystalline silicon are the ideal basis for photovoltaic systems. The solar cell efficiencies are still limited by the crystal defects (dislocations, grain boundaries) and their electrical activity. As a fast and efficient assessment of the electrical activity of specific...

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Bibliographic Details
Published in:Solar energy materials and solar cells 2002-04, Vol.72 (1), p.473-486
Main Authors: Barranco Dı́az, M, Koch, W, Häßler, C, Bräutigam, H.-G
Format: Article
Language:English
Subjects:
Applied sciences
Crystal orientation
Electric conductivity
Energy
Exact sciences and technology
Grain boundaries
Measurement
Natural energy
Photovolatic
Photovoltaic cells
Photovoltaic conversion
Silicon
Silicon wafers
Solar
Solar cells. Photoelectrochemical cells
Solar energy
Specific resistivity
Topography
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Summary:Solar cells made from multicrystalline silicon are the ideal basis for photovoltaic systems. The solar cell efficiencies are still limited by the crystal defects (dislocations, grain boundaries) and their electrical activity. As a fast and efficient assessment of the electrical activity of specific grain boundaries high resolution resistivity maps will be used, measured on a set of wafers as cut coming from the same block. Resistivity maps proved to be a precise and yet simple method to characterise grain boundary activity. While measurements in the bulk of the crystal are symmetric because of the isotropy of the material, measurements crossing rain boundaries are depending on the relative orientation of the boundary with respect to the measurement geometry. The large number of measurement points of a high resolution resistivity map allows a statistical treatment of the data to evaluate one quantitative value for the grain boundary electrical activity. Solar cells from those have been processed. In the regions with a higher electrical activity at grain boundaries, the open circuit voltage of the solar cell decreased. A specific evaluation of the electrical activity of grain boundaries on the basis of the thermionic model allowed the fine tuning of production parameters leading to a homogeneous quality of cast mc-Silicon wafers bearing the potential of approaching highest efficiencies in industrial production processes.
ISSN:0927-0248
1879-3398
DOI:10.1016/S0927-0248(01)00195-7