Purification of low quality silicon feedstock [for solar cell fabrication]

In the frame of the European ARTIST project, purification techniques have been developed that allow to use alternative silicon feedstock sources for PV production: (i) very low resistivity (0.08-0.1 /spl Omega/ cm) (VLR) silicon material was produced by directional solidification, resulting in solar cells of 14.5% efficiency; (ii) an inductive plasma purification unit was developed, demonstrating a significant reduction of B, P, C, O, Ca, and Al impurities from upgraded metallurgical grade silicon; and (iii) an Sb evaporation/condensation process was established to allow heavily doped n-type silicon feedstock to be used for PV, resulting in an average reduction of Sb by a factor of more than 100 after evaporation and directional solidification and in solar cell efficiencies above 15.5%. This paper summarises the technical state-of-the-art that has been achieved to date with respect to the above mentioned techniques.