Enhanced electrochromic performance of WO3 nanowire networks grown directly on fluorine-doped tin oxide substrates

Electrochromic devices have shown enhanced performances when constructed with nanostructured crystalline materials due to increased surface area and improved stability. A thin film of hexagonal WO3 nanowires was grown directly onto a bare fluorine-doped tin oxide glass (FTO) without the assistance of a WO3 seed layer via a facile and low-cost solvothermal method. Compared with the WO3 film synthesized with a seed layer, a faster switching time, higher coloration efficiency and more stable cycling were achieved due to direct nanowire contact with the substrate. In order to improve the contact between the WO3 and FTO, and therefore increase the stability of the electrode, it was annealed under N2 and the time of cycling stability increased by almost a factor of 10.