Study of gold doping in optical and electrical properties of tungsten trioxide thin films deposited by spray method

In this work, gold nanoparticle-doped WO₃ and nanostructured tungsten oxide (WO₃) thin films were produced via chemical spray pyrolysis. The process involved applying a thin layer of material to a glass substrate at 250 °C. The electrical and optical characteristics of films with different doping levels were ascertained using transmittance and absorbance spectra, electrical conductivity and resistivity tests, and so forth. The features of the un doped and doped films were then evaluated electrically in order to determine their conductivity, resistivity, charge carrier, and activation energy. The findings showed that Au was a major factor in film resistivity and that film resistivity decreased with increasing doping concentration. The films had a high NIR transmittance and were also semi-conductor. The formation of additional oxygen-deficient W₁₈O₄₉ phases may result in an increase in the density of oxygen deficit in the film, which could explain the observed decrease in band gap energy with more gold incorporation. Additionally, Au increased the refractive index because of crystallinity deterioration, which may alter the structure and bonding arrangement, and increased polarizability of the larger Au atomic radius relative to the W atomic radius.