Boosting the Zn2+-based electrochromic properties of tungsten oxide through morphology control

Zn2+-based electrochromic is a newly born technology in recent years and has attracted the attention of most researchers due to its low cost and high safety. The design of high-performance Zn2+-based electrochromic devices, such as large light modulation and fast color change, is still a challenge. Here, we report the improvement of Zn2+-based electrochromic properties by morphology control, using common electrochromic material WO3 as the research model. The hexagonal WO3 films with shape of nanorods and nanoflakes were prepared by hydrothermal method, where the diameter of the nanorods and the thickness of the nanoflakes are almost the same. The electrochromic characterization of WO3 nanorods and nanoflakes at 550 nm showed that their modulation ranges were 72.4% and 61.0%, their coloration times were 3 and 9 s, their bleaching times were 2.2 and 7 s, and their coloration efficiencies were 67.6 and 53.8 cm2 C-1, respectively. Compared with WO3 nanoflakes, the excellent Zn2+-based electrochromic properties of WO3 nanorods show rapid electron transfer kinetics caused by large surface area. Furthermore, the prototype electrochromic devices with WO3 nanorods were fabricated, which showed good specific capacitance and excellent electrochromic performance. The fast and large optical modulation synchronous as well as good energy storage makes the electrochromic device become a potential intelligent power supply. This morphology dependent electrochromic work provides a new vision for the construction of high-performance Zn2+- based electrochromic devices.