Comparison of optical absorption in Si nanowire and nanoporous Si structures for photovoltaic applications

Abstract

We numerically study the optical absorption in Si nanowire and nanoporous Si structures that have potential applications in solar cells. It is found that for the same thickness and filling ratio of Si, thin nanoporous structures can have much higher absorption than thin Si nanowire arrays. Above a critical filling ratio of Si (0.25), the nanoporous structures can have higher absorption even than thin films with the same thickness. For solar cells based on thin nanoporous Si structures, the maximal ultimate efficiency occurs when the filling ratio is around 0.3.