Micro/nano-hybrid hierarchical structure of black silicon decorated with gold nanoparticles for ultralow broadband reflectivity (<1%)

The antireflectance of black silicon is a critical factor in improving the performance of various optical and optoelectronic devices. Many efforts have been dedicated to reducing reflection by applying micro- or nanostructures to the silicon surface, but the predominant focus remains on wavelengths below 1100 nm. The antireflectivity of black silicon in the infrared range (>1100 nm) remains very weak because of the inherent material limitations. Here, a novel wafer-scale ordered micro/nano-hybrid hierarchical structure is proposed and prepared by two-step etching method, followed by decorating gold nanoparticles (Au NPs) randomly onto the structure via de-wetting process. Due to the synergy effect between the Au NPs-induced localized surface plasmon resonance (LSPR) and the hierarchical hybrid structure, the reflectance is dramatically suppressed. The Au NPs-decorated micro/nano-hybrid hierarchical structural scheme enables ultra-low broadband (300-2500 nm) antireflection with a total reflectivity of <1.0 %. Additionally, the transmittance of the sample is consistently maintained below 1.0 %, showcasing its exceptional absorption capability. Our strategy can efficiently and cost-effectively achieve tunable nanostructures at the 4 '' or 6 '' wafer scale, independent of silicon surface morphology, which has valuable applications in the field of sustainable energy, optoelectronics and microelectronics.