Ion-beam and plasma etching of a conical-pores photonic crystal for thin-film solar cell

Conical holes bored in the active layer of a thin-film silicon solar cell by ion-beam lithography (IBL) show increase of effective optical absorption in the underlying silicon active layer. The optical properties are numerically simulated by the 3D finite-difference time-domain method (3D-FDTD), showing wideband increase of the UV, visible, and IR quantum efficiency. An experimental fabrication procedure is developed using IBL for high wide-area repeatability. A further optimization on the cone shapes is performed in order to make fabrication feasible with plasma etching techniques.