Towards Specifications of n-type Silicon Purified via the Metallurgical Route

This study focuses on the fabrication and the characterization of solar cells using highly doped boron-phosphorus compensated n-type multicrystalline silicon. Two ingots were used and compared for this study. One ingot was crystallized from a silicon feedstock purified via the metallurgical route. The second ingot was crystallized from an electronic grade silicon feedstock in order to be metallic impurity free. Both ingots were intentionally compensated with a similar boron and phosphorus amount in the initial feedstock. Chemical and electrical characterizations were carried out on each ingot and similar carrier lifetimes were reported. Large area solar cells were fabricated on wafers selected at different positions along both ingots with a reference fabrication process leading to 18.4% efficiency on FZ material. No differences in terms of cells performances were observed between both ingots. Efficiencies between 13.5% and 15.0% were reported and were found to be limited by the low resistivity values of this material. This is consistent with the carrier lifetime previously measured which underlines the weak influence of the metallic impurities initially present in the wafers. Some perspectives are given in terms of feedstock specifications to exploit the potential of this material.