Electrochromic properties of Ni or Ti single-doped and Ni-Ag or Ti-Ag binary-doped WO3 thin films

In this paper, the single-doped (Ni-WO3 and Ti-WO3) and binary-doped (Ni-Ag-WO3 and Ti-Ag-WO3) amorphous WO3 thin films were respectively prepared on indium-doped tin oxide conductive glass substrates by radio-frequency magnetron sputtering. Among the single-doped WO3 thin films, the electrochromic (EC) properties of films can be enhanced by the presence of Ni or Ti. However, the low conductivity of WO3 limits its application in EC devices. A novel approach was proposed to ameliorate this disadvantage which has not been explored, that is, the highly conductive Ag was introduced into WO3 films with Ni or Ti. The experimental results show that the addition of Ag reduces the charge transfer resistance and shortens the ion diffusion path length, thereby improving the EC response time (Ni-Ag-WO3: tb=1.16 s; Ti-Ag-WO3:tc=4.14 s), electrochemical active area, and ion diffusion coefficients (Ni-Ag-WO3: Da =3.032 × 10−9 cm2/s; Ti-Ag-WO3: Dc=7.737 × 10−9 cm2/s). Based on these work, the feasibility of Ni-Ag and Ti-Ag binary-doped WO3 films was confirmed. These discoveries contribute to the exploration of preparing high-performance WO3 EC films for the practical applications of EC devices such as in automatic anti-glare rearview mirrors.