Silicon nanowire-based solar cells received increasing attention due to their enhanced light harvesting properties and the potential to use low-cost materials to produce solar cells comparable with those on costly monocrystalline counterparts. It is essential to improve the performance of nanowire solar cells by suppressing surface recombination. A multiple core (crystalline silicon nanowires)–shell silicon nanowire-based heterojunction solar cell has been fabricated to deal with this problem. To this end, an ultrathin passivating Al2O3 tunnel layer was deposited on the highly doped p-type a-Si:H emitter prior to a transparent conducting oxide by atomic layer deposition (ALD). Both open circuit voltage and current density increase significantly due to the insertion of the ultrathin Al2O3 layer. An efficiency of 10.0% has been reached by using this multiple core–shell structure.