Geometric dependence of antireflective nanocone arrays towards ultrathin crystalline silicon solar cells

Abstract

The antireflective characteristics of Si nanocone (NC) arrays were estimated using a theory devised for an inhomogeneous antireflection layer, and further verified by the Fourier modal method (FMM). Considering a better impedance matching from air to Si, a minimum depth of 400 nm is essentially required. Although Si NC arrays have usually been suggested to be at a base diameter of similar to 300 nm for infinitely thick Si wafers, as wafers become thinner than 50 mu m, the optimal base diameter of the NCs is suggested to be similar to 500 nm so as to excite more resonant modes. Our simulation work indicates that geometrical parameters such as the top diameter and filling ratio of the NCs are much more sensitive in terms of optimizing the optical performance on ultrathin (similar to 5 mu m) wafers, suggesting the need for strict control of the surface morphology in the nanostructure fabrication process.