Electrochromic properties of nanostructured tungsten oxide films prepared by surfactant-assisted sol-gel process

Pristine and surfactant F-127 added tungsten oxide films have been prepared successfully by sol-gel method using PTA as the precursor sol. After annealing at 300°C, amorphous WO₃ films with or without F-127 additions were prepared. The F-127-added tungsten oxide films exhibit porous microstructure, which are affected by the amount of F-127 addition. Nanosized microstructure with pore size less than 10nm can be observed with small amount of F-127 addition (less than 0.06g/ml) , where as larger spherical or tubular pores are found with superfluous F-127 addition (higher than 0.08g/ml). Not only the transmittance modulation but also the coloration efficiency can be improved by adding surfactant F-127. Tungsten oxide film with 0.10g/mlF-127 addition exhibits the best electrochromic performance with a transmittance modulation of 67.6% and a coloration efficiency of 38.3cm²C^-1.