Enhancement of Gettering in Epitaxial Thin-Film Silicon Solar Cells by Tuning the Properties of Porous Silicon

In epitaxial silicon solar cells grown on low-cost substrates, an embedded porous silicon layer is used to block metal diffusion from the substrate into the epitaxial active layer. The gettering efficiency of porous silicon can be enhanced by reducing the pore radius. In the size range (27.2 nm - 39.8 nm) investigated, the additional curvature of the 27.2 nm void leads to > 200 meV improvement in the binding energy for both copper and nickel, enhancing the gettering efficiency by > 10 times. This is due to the existence of specific binding sites which allows greater dangling bond passivation in smaller voids.