Antireflective hierarchical structures silicon fabricated via chemical etching assisted with femtosecond laser irradiation

Abstract

Silicon surface antireflection has attracted numerous research interests due to its wide range of applications in solar cell and optoelectronic devices. In this work, a chemical etching assisted with femtosecond laser irradiation method is proposed to fabricate antireflective hierarchical structures Si. Micro pyramids Si formed after KOH + IPA etching is used as intermediate to induce nanoparticles structures by fs laser irradiation. Micro pyramids reduce reflectance by trapping the incident light via multiple internals reflection mechanism, while nanoparticles reduce reflectance by effective medium layer effect and absorbance effect. It is found that at laser power of 2 mW, scan speed of 0.5 mm/s and scan interval of 20 μm, the hierarchical structures Si shows R<3.2 % in the wavelength of 400 nm–800 nm with average weighted reflectance of 2 %, lower than the reflectance of micro pyramid structures or nanoparticle structures. Besides, the fabrication process of hierarchical structures Si (with dimensions of 8 mm × 7 mm) is completed within 1.8 h (including chemical etching and fs laser irradiation), offering a new choice for the manufacturing of antireflective structures on silicon surface.