Investigation of charge recombination lifetime in γ-WO3 films modified with Ag0 and Pt0 nanoparticles and its influence on photocurrent density

In this communication, we report the growth of pure gamma-phase tungsten oxide (γ-WO3) films on a conducting substrate (fluorine-doped tin oxide), followed by heat treatment at 500 °C for 2 h, and finally modification with either silver (Ag0) or platinum (Pt0) metallic nanoparticles. These γ-WO3 thin films can be obtained from a tungsten citrate solution by a drop-coating method, and their surfaces are modified with Ag0 and Pt0 nanoparticles by photoreduction. X-ray diffraction analysis indicates that all the thin films have a monoclinic structure. Field emission-scanning electron microscopy analysis reveals large and fine grains for pure γ-WO3 film and modified WO3 films, respectively, with an average grain size of ~ 48 nm and thickness of ~ 986 nm. Finally, an enhancement in photoelectrochemical performance by a factor of ~ 2.5 is noted to modified γ-WO3 films, which is attributed to superior electron-hole charge recombination lifetime under polychromatic irradiation. It is observed that, even under bias, an exponential reduction in photocurrent intensity is associated with charge recombination instead of mass transport conditions like diffusion.