Enhanced electrochromic performance of 2D grid-structured WO3 thin films

Highlights: • Grid-structured tungsten trioxide (WO₃) electrochromic thin film was developed. • The grid structure enlarged transmittance modulation rate in redox reactions. • The grid structure also enhanced color efficiency and shortened response time. - Abstract: Controlling the microstructure of Tungsten trioxide (WO₃) film is believed to be an efficient strategy to enhance its electrochromic (EC) performance in recent years. Here, WO₃ thin films with two-dimensional (2D) grid structure are fabricated through electrodeposition using polystyrene (PS) nanofibers as sacrificial templates. The surface of WO₃ thin films has grooves formed by the removal of PS nanofibers and thus the films are divided into grid structure. Due to the larger specific surface area and lower diffusion impedance induced by the grid structure, these WO₃ films demonstrate an obvious enhancement of EC performance compared with the plane WO₃ thin films obtained using the same electrodeposition parameters in the absent of PS nanofibers templates. The transmittance modulation rate (ΔT) of the grid-structured WO₃ thin films is over 50% larger than that of the plane WO₃ films at the wavelength of 550 nm. Consequently, the grid-structured WO₃ films have a higher coloration efficiency (71.8 cm²/C) compared with the plane WO₃ films (58.8 cm²/C). Furthermore, the coloration/bleaching time of grid-structured WO₃ films are 1.27/0.93 s, which is much shorter than the plane WO₃ films (2.34/2.18 s). The grid-structured WO₃ films in this work show potential applications in the construction of highly performance and rapidly responsive EC devices.