This work covers some physical investigations on zinc-tin-oxide alloy thin films deposited on glass substrates at 450 °C by the spray pyrolysis technique. The effect of annealing in air on the physical properties of such films has been carried out. First, XRD analysis revealed good crystallinity of Zn-Sn-O as deposited film with presence of both Zn2SnO4 and ZnO phases. This was further supported by room temperature photoluminescence measurements showing the excitonic peaks for both phases, in addition to other peaks that are mainly due to both oxygen and zinc related defects. Second, the geometry optimization and the electronic properties of Zn2SnO4 were carried out using density functional theory (DFT) with corrected exchange correlation functional (PBE0) as implemented in the CRYSTAL14 code. The density of states indicates that the top of valence band is mainly built upon O-2p states whereas the bottom of the conduction band principally originates from Zn and Sn-5p states. Ab initio optimized structural parameters and electronic band structure conducted in this work shows a good agreement with our experimental data. Moreover, the hydropholic investigations have been carried out in terms of water contact angle (WCA) and reveal that these films have a hydropholic nature. Finally, the photocatalytic performances of both as deposited and annealed Zn-Sn-O thin films ones were investigated by degradation of aqueous methylene blue dye solutions under sunlight illumination for five hours. The results may be of interest for future sensitivity appkications like gas and bio-sensors.