Broadband antireflection on the silicon surface realized by Ag nanoparticle-patterned black silicon.

Broadband antireflection of silicon has been realized by combining black silicon, surface passivation and surface plasmons. Black silicon, fabricated by Ag assisted chemical etching, was employed here to reduce the reflection of incident light with wavelengths below 1100 nm. Due to the increased bandgap caused by the quantum confinement effect and enhanced backward-scattering in our black silicon, light trapping was diminished at the wavelengths above 1100 nm. Ag nanoparticles were deposited on black silicon to obtain the lowest reflectivity at the wavelengths above 1100 nm. Compared with traditionally textured multicrystalline silicon, the average reflectivity of passivated black multicrystalline silicon patterned with 5 nm mass thickness of Ag was decreased to 5.7% in the wavelength range from 300 nm to 1100 nm and was reduced by 20.2% in the wavelength range from 1100 nm to 1400 nm. The surface plasmon effect of the Ag nanoparticles on the black silicon was also demonstrated by surface enhanced Raman scattering, which was observed in the Ag nanoparticle patterned black silicon after being immersed in rhodamine 6g.