In this study, n -ZnO/ p -Si solar cells were fabricated by spraying ZnO nanoparticles ( NPs ) film synthesised by dissolving of high purity zinc in hydrogen peroxide H 2 O 2 followed by thermal oxidation in air on p -type silicon substrates. The oxidation was carried out at different temperatures (200–500)02°C. The crystalline structure of the ZnO NPs films was investigated by X-ray diffraction which indicated wurtzite structure films along (100) plane. The morphology of the NPs was studied by atomic force microscopy and scanning electron microscopy. The result showed an average grain size of ZnO NPs in the range of (72.7–95.8)02nm and the surface roughness increasing with oxidation temperature. Three peaks located at ultraviolet, violet and green emission regions were noticed in the photoluminescence spectra of ZnO NPs . From optical studies, it was shown that the direct optical band gap is found to be in the range of (3.85–3.96)02eV depended on the oxidation temperature. The synthesised ZnO films have n -type conductivity, and the mobility was in the range of (7–24)02cm 2 02V 611 02s 611 . Current–voltage I – V and capacitance–voltage C – V of ZnO NPs /Si heterojunction solar cell were investigated as function of oxidation temperature. The spectral response of n -ZnO NPs / p -Si solar cell showed two peaks of response and its maximum value approaching 0.6202mA02W 611 at λ 02=0280002nm. Solar cell oxidized at 50002°C gave open circuit voltage V OC of 37502mV, short circuit current density J SC of 2502mA02cm 612 , a fill factor FF of 0.72, and conversion efficiency η of 6.7902% under illumination of 10002mW02cm 612 .