Studies on electrochromic smart windows based on titanium doped WO3 thin films

Titanium doped tungsten oxide thin films have been deposited by co-sputtering metallic titanium and tungsten in the presence of argon and oxygen. The oxygen chamber pressure was varied in the range 1 × 10− 3–4 × 10− 3 mbar keeping the sputtering power of titanium and tungsten constant at 2 W/cm2 and 3 W/cm2 respectively. The effect of oxygen chamber pressure on the electrochromic (EC) properties of titanium doped WO3 has been investigated in three steps. First, the material properties of EC film were investigated by XRD, SEM, and UV–Vis spectrophotometer; the thickness and the optical constants were estimated from the reflectance measurements. Second, the electrochromic behavior of the EC films was characterized by cyclic voltammetry (CV) using 1.0 M HCl as electrolyte. The optical modulation (ΔT) and coloration efficiency (CE) of the titanium doped tungsten oxide thin film deposited at an O2 pressure of 4 × 10− 3 mbar was found to be better with typical values of ΔT  = 70% and CE = 66 cm2/C (at λ = 550 nm). Finally, EC devices consisting of five layers (Glass/ITO/Ti:WO3/Ta2O5/NiO/ITO) have been fabricated and tested.