A one-step template-free approach to achieve tapered silicon nanowire arrays with controllable filling ratios for solar cell applications

A facile and low-cost one-step template-free approach is presented for the fabrication of tapered silicon nanowire (SiNW) arrays. A silver network catalyst is used to chemically etch silicon in a HF/H2O2 solution, where the solution is chosen to selectively dissolve the silver network during the etching process, resulting in the formation of tapered SiNWs. Notably, the filling ratio of the tapered SiNWs can be tuned simply by varying the pattern of the silver network. Surface reflection was strongly suppressed in the tapered SiNW arrays (only 400 nm in thickness), which were employed in SiNWs/poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) heterojunction solar cells exhibiting a power conversion efficiency of 6.7%. The tapered SiNW arrays prepared by this one-step template-free method are expected to be efficient structures for a variety of photovoltaic devices.