Pulse Electrodeposition of Polycrystalline Si Film in Molten CaCl2 Containing SiO2 Nanoparticles

Abstract

<p>The high cost of Si-based solar cells remains a substantial challenge to their widespread adoption. To address this issue, it is essential to reduce the production cost of solar-grade Si, which is used as raw material. One approach to achieve this is Si electrodeposition in molten salts containing Si sources, such as SiO<sub>2</sub>. In this study, we present the pulse electrode-position of Si in molten CaCl<sub>2</sub> containing SiO<sub>2</sub> nanoparticles. Theoretically, SiO<sub>2</sub> nanoparticles with a diameter of less than 20 nm in molten CaCl<sub>2</sub> at 850°C have a comparable diffusion coefficient with that of ions in aqueous solutions at room temperature. However, we observed a slower-than-expected diffusion of the SiO<sub>2</sub> nanoparticles, probably because of their tendency to aggregate in the molten CaCl<sub>2</sub>. This led to the formation of a non-uniform Si film with low current efficiency during direct current electrodeposition. We overcome this issue using pulse electrodeposition, which enabled the facile supplementation of SiO<sub>2</sub> nanoparticles to the substrate. This approach produced a uniform and thick electrodeposited Si film. Our results demonstrate an efficient method for Si electrodeposition in molten CaCl<sub>2</sub> containing SiO<sub>2</sub> nanoparticles, which can contribute to a reduction in production cost of solar-grade Si.</p>