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Numerical simulation and fabrication of silicon sheet via spin casting.

Journal of nanoscience and nanotechnology (2013-07-19)
Jaewoo Lee, Hyunhui Kim, Changbum Lee, Joonsoo Kim, Bo-Yun Jang, Jinseok Lee, Youngsoo Ahn, Wooyoung Yoon
ABSTRACT

A spin-casting process for fabricating polycrystalline silicon sheets for use as solar cell wafers is proposed, and the parameters that control the sheet thickness are investigated. A numerical study of the fluidity of molten silicon indicates that the formation of thin silicon sheets without a mold and via spin casting is feasible. The faster the rotation speed of graphite mold, the thinner the thickness of sheet. After the spread of the molten silicon to cover the graphite mold with rotation speed of above 500 rpm, the solidification has to start. Silicon sheets can be produced by using the centrifugal force under appropriate experimental conditions. The spin-cast sheet had a vertical columnar microstructure due to the normal heat extraction to the substrate, and the sheet lifetime varied from 0.1 microS to 0.3 microS measured by using the microwave photoconductance decay (MW-PCD) to confirm that the spin-cast silicon sheet is applicable to photovoltaics.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Silicon, pieces, 99.95% trace metals basis
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Silicon, wafer (single side polished), <111>, P-type, contains boron as dopant, diam. × thickness 3 in. × 0.5 mm
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Silicon, wafer (single side polished), <100>, N-type, contains no dopant, diam. × thickness 3 in. × 0.5 mm
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Silicon, wafer (single side polished), <111>, N-type, contains no dopant, diam. × thickness 3 in. × 0.5 mm
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Silicon, wafer (single side polished), <111>, N-type, contains phosphorus as dopant, diam. × thickness 2 in. × 0.5 mm
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Silicon, wafer (single side polished), <100>, N-type, contains phosphorus as dopant, diam. × thickness 3 in. × 0.5 mm
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Silicon, wafer (single side polished), <100>, N-type, contains phosphorus as dopant, diam. × thickness 2 in. × 0.5 mm
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Silicon, wafer, <111>, P-type, contains boron as dopant, diam. × thickness 2 in. × 0.3 mm
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Silicon, wafer (single side polished), <100>, N-type, contains no dopant, diam. × thickness 2 in. × 0.5 mm
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Silicon, wafer (single side polished), <111>, N-type, contains no dopant, diam. × thickness 2 in. × 0.5 mm
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