In this article are investigated the optical and structural properties of copper oxide thin films deposited by ultrasonic spray pyrolysis and the effect of the substrate temperature and the D-sorbitol precursor solution reducing agent. The Cu2O/CuO phase transition, a key factor for the development of this metal oxide for photovoltaics and other applications, is studied using X-ray diffraction, confocal micro-Raman and transmittance spectroscopy. The obtained structural and optical properties are correlated to analyze the phase transition and the effect of the reducing agent concentration combined to the controlled and precisely defined preparation temperature. The study permitted to use a relatively low preparation temperature of 230 °C to produce a single Cu2O phase using the D-sorbitol reducing agent. The optimized structural and optical properties were obtained without the need of using D-sorbitol in excess compared to copper acetate, as usually done when using glucose, thereby reducing the density of defects and improving electrical properties for optoelectronic applications.