Black silicon with order-disordered structures for enhanced light trapping and photothermic conversion

Abstract Black silicon has become a versatile substrate for photoelectric and photothermic application due to its excellent light trapping ability. However, subsequent material engineering can conflict with its intrinsic anti-reflective behavior. In this paper, we present a two-step etching approach to create novel black silicon combining ordered micropores and disordered nanopores. The larger pores increase the optical path length and provide space to load functional materials, while the smaller ones facilitate coupling between the incident solar radiation and material. The proposed etching method increases the light-trapping ability of conventional nanostructured black silicon and achieves enhanced absorption in a broad spectrum. Besides, loading Au nanoparticles further improve the light absorbance in the near-infrared range of 1100–1700 nm. The intrinsic SiOx-rich layer on silicon surface produced during SF6/O2 plasma etching leads to photothermic conversion being the dominant dissipation route for the light energy, thereby yielding outstanding performance in photothermic and photo-thermal-electric demonstrations. This work establishes a robust relationship between three-dimensional structure and light-trapping property of black silicon and provides insights into substrate designs that facilitate the light conversion.