Angle-resolved characteristics of silicon photovoltaics with passivated conical-frustum nanostructures

Passivation plays a critical role in silicon photovoltaics, yet how a passivation layer affects the optical characteristics of nano-patterned surfaces has rarely been discussed. In this paper, we demonstrate conical-frustum nanostructures fabricated on silicon solar cells using polystyrene colloidal lithography with various silicon–nitride (SiNx) passivation thicknesses. The omnidirectional and broadband antireflective characteristics were determined by utilizing angle-resolved reflectance spectroscopy. The conical-frustum arrays with a height of 550 nm and a SiNx thickness of 80 nm effectively suppressed the Fresnel reflection in the wavelength range from 400 to 1000 nm, up to an incidence angle of 60°. As a result, the power conversion efficiency achieved was 13.39%, which showed a 9.13% enhancement compared to that of a conventional KOH-textured silicon cell. The external quantum efficiency measurements confirmed that the photocurrent was mostly contributed by the increased optical absorption in the near-infrared. The angular cell efficiencies were estimated and showed improvements over large angles of incidence.