Reducing the Surface Area of Black Silicon by Optically Equivalent Structures

Black silicon is a promising low-cost technology to boost the efficiency of solar cells. The large surface area of black silicon, however, imposes challenges such as increased surface recombination and Auger recombination in doped nanostructures. This issue motivates the search for structures with lower surface area but similar optical properties. Here, we identify an approach for reducing the surface area of black silicon, while maintaining optical performance. Specifically, we have demonstrated via simulations that wavelength-scale arrays of nanotapers have similar antireflection properties as black silicon, but with less than half of the surface area. Additionally, we highlight that the light-trapping properties of black silicon are not optimal, and that its performance can be further improved by using nanostructures with controlled scattering properties. We quantify the optical performance of the structures and their surface area, thus identifying optically equivalent structures with reduced surface areas. We believe that these findings will help to boost the efficiency of devices based on black silicon.