The effect of the crystal lattice mismatch between single p-GaAs nanowire grown on p-Si substrate on the solar cell efficiency is studied. The study is performed by measuring the IV curves under red (wavelength=650 nm) laser illumination. The measurement of the single nanowire was done by conductive atomic force microscopy (C-AFM). The measured curve was reproduced by numerical simulations accounting piezoresistance and piezoelectric effects. The analysis demonstrated the presence of the tensile (2%) zinc blend insert at the interface between nanowire and substrate induced by crystal lattices mismatch. Strained insert at the interface changes the polarity of the photogenerated current and increases the efficiency by 2 times.