The core-shell nanocomposites of titanium dioxide (TiO2) and nickel oxide (NiO) used as modified photoelectrode materials in a quasi-solid-state dye-sensitized solar cell (quasi-DSSC) were synthesized using TiO2 P-25 and a nickel acetate precursor, via ball milling. The as-obtained intermediate products were annealed at 350, 450, and 550 degrees C. The structural properties of the NiO/TiO2 nanocomposites were well characterized via X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The results imply that NiO-shell-coated TiO2 nanoparticles can be obtained with the assistance of sufficient thermal energy in the system. The crystallite size of the composite increased as the annealing temperature increased. Among all the prepared conditions, the composite with 0.1 wt% NiO exhibited the best performance, with an optimized solar-energy conversion efficiency of 2.29% and with a short-circuit current density of 7.21 mA/cm2. The significant enhancement of the device's current density may be associated with the charge recombination suppression by the NiO shell, which acted as a potential barrier in the composite. The decrease in the recombination of the photo-injected electrons, and the increase in the number of electrons tunneling through the NiO layer at the interface, may have resulted from the presence of a NiO layer on the TiO2 nanoparticles.