Improving Electrochromic Properties of WO3 Thin Film with Gold Nanoparticle Additive

In this research, WO3 and Au-WO3 thin films were prepared at different temperatures using the sol gel method. The effect of gold nanoparticles (GNPs) on the electrochromic properties of W 3 was also studied. 2.5 nm GNP was synthesized through sodium citrate reduction of gold chloride in an aqueous solution. These films were characterized by XRD, SEM, TEM, and spectrophotometer analyses. The films annealed at 200˚C were amorphous and crystallized at high temperatures. According to the scanning electron microscopy (SEM) image, the films annealed at 200˚C were dense. Moreover, the particles were uniformly distributed on them. Spectrophotometer analysis of WO3 thin films annealed at 200˚C showed high electrochromic properties (transmission modulation (ΔT) was 72% and response time was 3.25s for 80% coloring). Spectrophotometer analysis of Au-WO3 thin films annealed at 200˚C showed that their coloration properties increased (ΔT = 78%) and response duration decreased (1.65s) when gold nanoparticles were added. This enhancement is attributed to the increased conductivity caused by the addition of gold nanoparticles as well as the surface plasmon resonance based absorption of GNPs.