Investigation of effective near-infrared light-trapping structure with submicron diameter for crystalline silicon thin film solar cells

Abstract

To obtain high efficiency in crystalline silicon thin-film solar cells, it is necessary to develop a novel light-trapping structure that not only has high light absorptance and can be fabricated with a small etching margin but also has a small surface area for a small effect of surface recombination. In this study, optical properties of silicon nanowires (SiNWs) with submicron diameters were investigated by the finite-difference time-domain (FDTD) method in the infrared wavelength region, in which the absorption coefficient of crystalline Si is quite low and the increase in optical path length is very important. To verify the simulation results, SiNWs with submicron diameters were successfully fabricated by the metal-assisted chemical etching method using two types of etching masks. The optical properties and minority carrier lifetime of the obtained structures were measured, and the results suggest that SiNWs with submicron diameters such as ∼700 nm are effective for both light trapping and the suppression of surface recombination.