Silicon nanowire solar cells with heterojunctions were prepared on single crystalline silicon wafers. The nanowire arrays were generated by silver catalyzed etching of n-type wafers. After careful removal of the metallic silver particles a p-doped amorphous silicon shell was deposited around the nanowires by PECVD, which served as a heteroemitter. Then a transparent conductive oxide (aluminum doped zinc oxide) layer was deposited by atomic layer deposition which filled the space between the nanowires. The cells were characterized by SEM, TEM, and EBIC. Under AM1.5 illumination an open circuit voltage of 476 mV and an efficiency of 7.3% was observed on a cell of 7 mm² area.