Relationship between oxygen impurity distribution in multicrystalline solar cell silicon and the use of top and side heaters during manufacture

• Published in: Journal of crystal growth 2013-07, Vol.375, p.62-66
• Main Authors: Nakano, S., Gao, B., Kakimoto, K.
• Format: Article
• Language: English
• Subjects: A1. Computer simulation; A1. Directional solidification; A1. Impurities; Applied sciences; B2. Semiconducting silicon; B3. Solar cells; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crucibles; Defects and impurities in crystals; microstructure; Energy; Exact sciences and technology; Growth from melts; zone melting and refining; Impurities: concentration, distribution, and gradients; Materials science; Methods of crystal growth; physics of crystal growth; Natural energy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Photovoltaic conversion; Physics; Solar cells. Photoelectrochemical cells; Solar energy; Solidification; Structure of solids and liquids; crystallography
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2013.04.001

The relationship between the oxygen impurity distribution in multicrystalline silicon and the use of top and/or side heaters in an unidirectional solidification process was investigated by numerical analysis. It was found that the oxygen concentration in the melt for the side heating system is lower than that for only the top heating system. This occurs because of the difference in flow direction of the melt near the crucible wall. The melt flows upward near the crucible wall when the side heating system is used. Oxygen is therefore dissolved from the silica crucible wall and is transported easily to the melt surface, where it evaporates. •Influence of heater location on oxygen concentration is studied by simulation.•Evaporation flux of oxygen depends on oxygen concentration at the melt surface.•Flow direction near crucible wall controls oxygen concentration at the melt surface.•Heater location controls flow direction.•Oxygen concentration at the melt surface is larger for side heater location.