Electrochromic Properties of RF-Sputtered WO₃ Films: An Impact of Post-annealing and Room Temperatures for Smart Window Applications

Tungsten oxide (WO₃) thin films were deposited on glass substrates of Corning glass (CG) and fluorine-doped tin oxide (FTO) using an RF magnetron sputtering process. The effects of varying the annealing temperature on structural, surface morphology, optical properties, and electrochromic (EC) are examined using X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), SEM, Raman spectroscopy, UV-Vis spectroscopy, and cyclic voltammetry. WO₃ thin films annealed at 573 K and 673 K were shown by SEM analysis to have fewer cracks after being found to crack more at 773 K. According to the XRD investigation, the WO₃ thin films annealed at 573 K, 673 K, and 773 K had a crystalline nature. At 773 K, when the coloring efficiency (CE) was determined to be 40.45 cm²/s, the diffusion coefficient was found to be the lowest (1.7 × 10⁻¹⁴ cm²/C). At 573 K, the coloring efficiency (CE) was measured to be 52.38 cm²/C, and at 673 K, it was 39.33 cm²/C. It has been discovered that post-annealing significantly affects color efficiency, which is important in electrochromic (EC) applications.