Enhancing Photoelectrochemical Energy Storage by Large-Area CdS-Coated Nickel Nanoantenna Arrays

The integration of thin films made up of periodic plasmonic nanostructures and semiconductors holds great potential to develop efficient technologies for photoelectrochemical solar energy conversion and storage. However, to date, only periodic nanoantenna arrays made up of Au have been explored, posing severe limitations in terms of scalability and costs. Here, we show that nickel nanopillar arrays can support complex electromagnetic resonances that strongly enhance the photoelectrochemical response of CdS thin films. By controlling the pitch size and diameter of the nanopillars, we obtain broadband light absorption from the ultraviolet (UV) to the near-infrared (NIR) wavelength range, thus achieving large photocurrent enhancements compared to a planar Ni/CdS sample and in line with those generated by previously reported Au nanostructures. The photocurrent enhancement is attributed to photonic modes in the UV and hybrid cavity-plasmonic modes in the visible and NIR ranges, which give rise to efficient energy transfer and hot carrier injection between metallic structures, the semiconductor, and the electrolyte. The developed nanopillar arrays are promising candidates for photoelectrochemical devices fully exploiting the solar spectrum and using Earth-abundant raw materials.