Comparative investigation of the Ti and Mo additives influence on the opto-electronic properties of the spray deposited WO3 thin films

As opposed to Ti-doping which has a detrimental effect on layers structure, Mo addition, even in high concentrations, has a positive effect on layers crystallinity; hence higher conductivity and ideality factors close to 1 are obtained for these films. Surprisingly, Ti and Mo-WO3 films contain cation additives also in lower oxidation states, 3+ and 5+, respectively, compared to the ones in the precursor salt. A 2 at.% Ti concentration is enough to significantly improve the photoconductivity of the WO3 films, whereas for Mo addition higher levels are needed (10 at.%). The Ti and Mo-WO3 films have high transparency with average transmission values of 85% and 75%, respectively. The thin films reflectance decreases with increasing doping concentration along with roughness diminution.