SBIR Phase I: Low-cost clean one-step production of solar silicon from natural quartzite

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project will be the reduction of silicon in PV modules from 4¢/W to 0.8-1¢/W. Besides considerable silicon price reduction, this novel technology removes currently presented safety and environmental concerns of silicon production. Decreasing the total PV module cost will improve access to solar cells, through which the overall consumption of fossil fuels could be reduced. Moreover, since this novel technology is zero direct GHG emission, replacing the current manufacturing processes with our new technology can positively affect the environment directly and immediately. This project will also advance the state-of-the-art in silicon manufacturing and provide a domestic source of PV quality silicon. This project aims to develop a new molten salt electrolysis process which can produce solar silicon from natural 99.7-99.9% pure quartzite (SiO₂) in just two steps, replacing a complex energy-intensive five-step process today. This process utilizes a state-of-the-art molten salt composition with a new mechanism for suppressing dendrite formation and salt trapping. This process can potentially produce silicon with 4-5N purity at $1.70/kg using <30 kWh/kg, with pure oxygen by-product and zero direct Greenhouse Gas (GHG) emissions. The 4-5N product purity would be sufficient for directional solidification or direct boule/wafer production, resulting in $2.20-2.70/kg solar-grade silicon cost, i.e., 75-80% lower than today. This purity through the novel process is achievable via electrochemical selection, an inert anode to avoid carbon anode contamination, and low impurity solubility in the solid silicon product. The technical issues/risks to be addressed in this proposal are salt trapping to practically produce dense and pure product, removing more electronegative impurities (P, Fe) that cause problems with carrier lifetimes, and utilizing magnetohydrodynamics (MHD) stirring to overcome stagnant electrolyte bath. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.