Flexible omnidirectional and polarisation-insensitive broadband plasmon-enhanced absorber

We demonstrate a facile method to fabricate Ag-Sb₂S₃ nanoporous plasmonic absorbers on plastic, crystalline, and glassy substrates. Our lithography-free method exploits the immiscibility of Ag and Sb₂S₃ to control the surface morphology of the absorbing structure. We experimentally and theoretically show that the nanoporous structure exhibits a high absorption across the visible and near infrared spectrum, which is achieved by the coalescence of surface/bulk plasmons and the Sb₂S₃ semiconductor bandgap absorption. The absorptance is independent of polarisation over a broad range of incident angles. We found that the Ag-Sb₂S₃ nanoporous structure is an effective absorber on both flexible and non-flexible substrates, and the simple deposition of the Ag-Sb₂S₃ nanoporous structure facilitates fabrication over a 100 mm diameter wafer. Our work shows that plasmonic nanostructures can be fabricated at room temperature on an industrial scale using sputtering, which is already used to commercially produce photovoltaic cells. We foresee these inexpensive absorbers being applied to wearable light-harvesting systems, bio-sensing, and display technologies.