To improve the productivity of a photovoltaic (PV) module, TiO₂ thin films of different thicknesses were applied as a self-cleaning layer on soda-lime glass and a Si PV module by spray-coating a TiO₂ solution. The structural, optical, and wettability characteristics of the TiO₂ thin films were investigated with respect to the thickness. Thermogravimetric-differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, contact-angle analysis, ultraviolet-visible spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and a solar simulator were used to analyze the prepared TiO₂ thin films. The optimal thickness was determined to be 100 nm. The TiO₂ thin film exhibited a self-cleaning ability even after post-annealing at 250 °C. After the self-cleaning ability was confirmed, the TiO₂ thin film was applied to the PV module.