Effect of substrate pre-treatment on controllable synthesis of hexagonal WO3nanorod arrays and their electrochromic properties

Abstract

Hexagonal WO₃ nanostructures with controlled sizes and alignment ordering have been successfully realized on fluorine doped tin oxide (FTO) substrates with different pre-treatment methods by a hydrothermal approach. The effects of the pre-treatment conditions, such as pre-coating a layer of WO₃ nanoparticles, the annealing temperature and time and the colloid concentration, on the orientation and morphology of the WO₃ nanorods were systematically investigated by scanning electron microscopy and X-ray diffraction. The WO₃ nanorod arrays (WNRs) vertical to the FTO substrate and spindle-like nanorod bundles parallel to the FTO substrate can be selectively prepared depending on the crystallinity and the density of the WO₃ seeds pre-coated on the FTO substrates. Moreover, the influence of the as-prepared WO₃ morphology on its electrochromic (EC) property was also discussed.