Effect of laser power density on the electrochromic properties of WO3 films obtained by pulsed laser deposition

Pulsed laser deposition (PLD) was used to prepare tungsten trioxide (WO 3 ) films on ITO substrates with a varying laser power density of 4.0–5.5 W/cm 2 . XPS indicated that when the laser power density decreased, the peak positions of the W 4f and O 1s orbits shifted slightly to low energy due to the difference in oxygen vacancies. As the laser power density decreased, W 6+ gradually replaced the lattice position of O 2− , increasing oxygen vacancies in the lattice. The transmittance modulated values ( ΔT ) were over 44% at 830 nm, indicating strong absorption by the WO 3 thin films in the near-infrared ray. The switching time of the WO 3 thin films between bleached states and coloured states decreased as the laser power density increased due to the amorphous structure, morphology, and lower oxygen deficiency at a high power density. The high ΔT and very fast switching time of t b (1.09 s) and t c (6.01 s) demonstrated the excellent electrochromic (EC) properties of the WO 3 films prepared by PLD.