Electrochromic films with a stacked structure of WO₃ nanosheets

Electrochromic films with a stacked structure of two-dimensional crystalline tungsten trioxide (WO₃) nanosheets were fabricated on fluorine-doped tin oxide (FTO) coated glass by a layer-by-layer (LBL) technique. Unique electrochromic property with a slow coloration process but a fast bleaching process was observed during the insertion/extraction process of the protons into/from the stacked structure. The linear relationship between the anodic peak current density and the square root of the potential sweep rate, indicating the insertion/extraction process of the protons into/from the stacked structure is controlled by a diffusion mechanism. The nanosheet film also exhibits a coloration efficiency of 32 cm²/C and an excellent long-term stability during the electrochromic process.