We reported the fabrication of an FTO conducting thin film via a spray deposition method, which was used to investigate the effect of oxygen content in the carrier gas on deposited film morphology and properties. Using a carrier gas containing various O2/N2 concentrations (0%, 20%, 50%, 80%, and 100%) led to significant changes in the thickness, size, and shape of grain growth. The deposited films with 0-50% oxygen content yielded a low resistivity of ∼10∼4 52-cm and a transmittance in the range of 76-96% at 550 nm. Furthermore, by changing the carrier gas concentration, the FTO films displayed different charge transport, recombination, and collection properties due to the surface and interfacial effects. These films with modified properties can be applied to dye-sensitized solar cells (DSSCs). Overall, the conversion efficiency of a solar cell based on a 0% O2 sample was increased by approximately 2% from that of a 100% O2 sample. The higher efficiency is mainly the result of the lower O2 content, which minimized the grain boundaries (spacing) and improved the electron transport on the FTO film surface.