Hierarchical tungsten oxide flower-rod architectures synthesized by hydrothermal route and its applications in electrochromism

A hierarchical tungsten oxide flower-rod architecture, which provides additional active sites for redox in electrochromic devices (ECDs), was prepared by hydrothermal method. WO 3 electrochromic (EC) thin films were prepared by spin-coating, and their electrochromic ability and electrochemical properties were measured. The complete oxidation of the electrochromic layer in the electrochromic device was promoted due to the large surface of the layered flower-rod structure providing active sites for ion transfer, resulting in a yellow–brown color in the bleached state (2.6 V) and a grey-blue color in the colored state (− 2.6 V). In addition, tungsten oxide with a hierarchical flower-rod structure exhibits good electrochemical stability. This work investigates the link between ionic redox efficiency and multicolor electrochromic performance, paving the way for the design of multicolor ECDs with a single inorganic EC layer.