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. The essential to improve the performance of nanowire solar cells is to suppress 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.