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 (WO3) 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, W6+ gradually replaced the lattice position of O2-, increasing oxygen vacancies in the lattice. The transmittance modulated values (Delta T) were over 44% at 830 nm, indicating strong absorption by the WO3 thin films in the near-infrared ray. The switching time of the WO3 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 Delta T 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 WO3 films prepared by PLD.