Impact of defect distribution and impurities on multicrystalline silicon cell efficiency

The material properties of several commercially available multicrystalline silicon ingots are analysed, and their relation with cell efficiency is evaluated. Three aspects are clearly correlated to the cell results. i) Fe contamination, in particular the excessive contamination at the edge of ingots; ii) oxygen contamination, deteriorating the properties in the bottom of some ingots, and iii) distribution of minority carrier lifetime in wafers, which is correlated to the crystal defect density. With consideration of these aspects, the variation of cell properties within an ingot, and to a lesser extent between ingots, can be understood.