With the very high efficiency that has been achieved in silicon-based solar cells, the international technology roadmap for photovoltaics foresees a steady decrease in the thicknesses of such cells over the next decade. In this paper, we present an ultrathin interdigitated back-contacted silicon solar cell fabricated using 30-mu m-thick Si substrates. In consideration of the special light-trapping and passivation requirements for ultrathin wafers, Si nanowire arrays coated with Al2O3 were used to significantly reduce the reflectance in the visible region of the solar spectrum. The 15-nm-thick conformal Al2O3 coating improved the effective minority carrier lifetime of the silicon nanowires and exhibited competitive passivation performance. Furthermore, the photovoltaic properties of the fabricated ultrathin solar cell were investigated and a relatively high conversion efficiency of 16.61% was determined for a thickness of 30 mu m. The findings of this study confirm the feasibility of producing ultrathin silicon-based photovoltaic devices. (c) 2015 Published by Elsevier Ltd.