Nanotexturing Process on Microtextured Surfaces of Silicon Solar Cells by SF6/O2 Reactive Ion Etching

We investigated a nanotexturing process on the microtextured surface of single crystalline silicon solar cell by the reactive on etching process in SF6/O-2 mixed gas ambient. P type Si wafer samples were prepared using a chemical wet etching process to address saw damage removal and achieve microtexturing. The microtextured wafers were further processed for nanotexturing by exposure to reactive ions within a circular tray of wafer carrier containing many small holes for uniform etching. As the dry etching times were increased to 2, 4 and finally to 8 min, surface structures were observed in a transition from nanoholes to nanorods, and a variation in wafer color from dark blue to black. The surface nanostructures showed a lowered photoreflectance and enhanced quantum efficiency within the visible light region with wavelengths of less than 679 rim. The nanohole structure etched for 2 min showed enhanced conversion efficiency when compared to the bare sample: however the nanorod structure etched for 8 min exhibited the decreased efficiency with a reduced short circuit current. indicating that the surface nanostructural damage with the enlarged nanoperimetric surface area is sensitive to surface passivation from the surface recombination process.