Optimization of Opto-Electrical and Photocatalytic Properties of SnO2 Thin Films Using Zn2+ and W6+ Dopant Ions

A series of Zn2+ and W6+ doped tin oxide (SnO2) thin films with various dopant concentrations were prepared by spray pyrolysis deposition, and were characterized by X-ray diffraction, atomic force microscopy, contact angle, absorbance, current density-voltage (J-V) and photocurrent measurements. The results showed that W6+ doping can prevent the growth of nanosized SnO2 crystallites. When Zn2+ ions were used, the crystallite sizes were proved to be similar with the undoped sample due to the similar ionic radius between Zn2+ and Sn4+. Regardless of the dopant ions' type or concentration, the surface energy has a predominant dispersive component. By using Zn2+ dopant ions it is possible to decrease the band gap value (3.35 eV) and to increase the electrical conductivity. Photocatalytic experiments with methylene blue demonstrated that with zinc doped SnO2 films photodegradation efficiencies close to 30% can be reached.