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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Boron and Phosphorus in Solar Grade Silicon

Awarded: NOK 12.1 mill.

The growth of the solar cell market, indicates a shortage of solar cell feedstock silicon at present and in the near future. Therefore, creation of special technologies of this feedstock production is necessary. The most direct approach for silicon feedst ock production is to upgrade metallurgical-grade (MG) silicon, but cost effective reduction of Boron and Phosphorus has not been possible so far. In the metallurgical process, which is a new route for silicon refining, MG silicon is purified through slag treatment, leaching of solidified silicon particles, and solidification refining. Directional solidification is a key stage in the metallurgical refining process. In this stage most of the impurities are properly removed due to their low segregation coeff icients. However, B and P are the problematic elements and they cannot be effectively removed due to their high segregation coefficients. Therefore, it is necessary to do additional refining process focused on removing B and P from MG silicon as much as p ossible prior to the directional solidification. In the present project the refining of metallurgical grade silicon is carried out focusing on B and P removal by slag treatment and plasma technique. An extensive literature survey on the refining of metall urgical grade silicon, and some theoretical studies on the thermodynamics of B and P removal from the silicon will be done. Characterisation techniques for measuring B and P concentrations in Si at very low levels (sub-ppm) will be evaluated, and even a t est method will be developed. The project will be done through a collaboration between NTNU and foreign institutes with researcher and student exchanges. Some journal and conference articles and also PhD thesis and some scientific reports will be prepared through this project.

Funding scheme:

FRINATEK-Fri prosj.st. mat.,naturv.,tek