Performance of Modules and Solar Cells Made of 100% Solar Silicon Purified by Direct Route

E. Forniés, A. Souto, T. Vlasenko, A. Pérez Vázquez, M. Tojeiro, M. Anoshenko, G. Varela

After several years of research, FerroSolar has designed a novel but mature process that is able to purify the metallurgical grade silicon (MeG-Si) from 2 nines up to 6 nines of purity. An important step forward has been the capability of the process to reduce the phosphorous and boron concentration down to a level where compensation is enough to obtain a resistivity within the standard parameters of solar cell producers ( = 1-3 Ω·cm). This resistivity has been achieved with furnace charges of 100% solar silicon (or UMG). This paper describes the process followed by the solar silicon along the whole value chain, showing the outcomes in each step. MeG silicon has been purified in a multi-step process that involves, the usage of slags and vacuum purification, obtaining the solar grade silicon. Then multi-crystalline ingots were grown by high performance multi process (HPM). The wafers were sent to a solar cell and module producer where underwent through and standard process of manufacturing according to Al-BSF technology. Solar cells of up to 18.84% efficiency and modules of up to 333 W were obtained. This performance is particularly high, considering that no high efficiency technologies have been applied to the cell manufacturing.