Effects of morphology, size and crystallinity on the electrochromic properties of nanostructured WO3 films†
WO3 nanostructures with various morphologies and crystallinity (such as cylinder-like WO3 nanorod arrays (WNRs-1), porous WO3 nanofibers, WO3 nanoflake arrays, sharp cone-like nanorod arrays (WNRs-2) and annealed cylinder-like WNRs-1) were prepared on FTO substrates by using a hydrothermal method without organic additives. The effects of morphology, size and crystallinity on the electrochromic properties of WO3 nanostructures were systematically investigated by scanning electron microscopy, X-ray diffraction, cyclic voltammetry and chronoamperometry. WNRs-1 exhibited excellent cyclic stability, wide optical modulation (64%), and relatively high coloration efficiency (61 cm2 C−1). Fast switching speeds of 5 s and 6 s for bleaching and coloration are achieved for WNRs-1 after annealing. Moreover, the relationship between the micro-morphologies/structures and electrochromic performance of WO3 nanostructures was also discussed.