Light-trapping structures are fabricated on crystalline (100) silicon (c-Si) surfaces by picosecond (ps) laser irradiation followed by chemical etching. First, 1064-nm ps laser scanning is used to form micropore arrays on c-Si. The ps laser processing causes little reconsolidation of the silicon surface, which is beneficial to achieve precise etching. Control of the laser scanning interval, number of scans, and etching time gives a micro-nano hierarchical structure. In this hierarchical structure, the average diameter of the micropores is 25 to 30 μm, while the size of the finer nanostructures on the micropore inner walls ranges from dozens to hundreds of nanometers. Unlike traditional laser texturing techniques, the whole laser process is carried out without mask and photolithography. The reflectance of the c-Si surface with a micro-nano hierarchical structure is as low as 6% in the wavelength range from 400 to 1000 nm without coating. Moreover, the samples also show good hydrophobicity. This is a potential method to fabricate economical antireflective structures that are ideal for applications in c-Si solar cells and self-cleaning c-Si microelectronic devices.

The fabrication of porous silicon with double band photoluminescence (PL) by chemical-assisted 1064 nm picosecond (ps) laser irradiation of polysilicon is presented. The hybrid method includes controlling of the laser scanning interval, number of scans to form dense micropores, and subsequently, short-time acid corrosion to form fine nanostructure. Along with the stable red PL visible to the naked eye, a new violet PL band at 432 nm existed in the fabricated samples. The double band photoluminescence was mainly attributed to the prepared micro/nano hierarchical structure. Moreover, dangling bond defects formed by high-energy photon impinging acted as the catalyzer in the subsequent acid corrosion resulted in good passivation of the nanostructure with the formation of Si-H and Si-O bond, which also contributed to the stable photoluminescence. The maximum surface porosity of the samples was concluded to be 90.48% which also bring good hydrophobicity for the prepared samples.

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