Solar cells based on nanowire (NW) array has shown promising potential for the low cost photovoltaic because of light absorption and charge carrier transport in this structure are in orthogonal direction to each other. In this study, we report the effect of variation of doping and defect densities on vertical NW solar cell bench-marked with standard planar structure using 3D-TCAD simulation. The performance of NW and planar structure for different amount of defect densities in the structures is investigated. We show that performance of NW solar cell continuously increases with wire doping. The results show that for increased efficiency, a high p-core and n-shell doping densities (∼10 19 cm -3) are needed. This is attributed to radial structure of NW and increased field assisted charge separation. It is found that for same amount of illuminated area, NW structure has 25% higher conversion efficiency. Further it is found that NW radial structure can tolerate defect density as high as 10 18 cm -3, with 82% higher conversion efficiency than planar structure. Our results have significant importance for design of vertical NW based solar cells and applications.