Fig. 1. 500 nm thick WO₃ film deposited on ITO glass substrate. (a) Scanning electron microscope (SEM) surface morphology; (b) SEM cross-sectional morphology; (c) XRD spectra

Fig. 2. Initial optical properties of WO₃ films under different electrolyte concentrations. (a) Transmittance spectra; (b) modulation rate comparison at λ=550 nm

Fig. 3. Initial response time of WO₃ films under different electrolyte concentrations. (a) CA curves; (b) response time and comparison

Fig. 4. Initial CV cycle curves of WO₃ films under different electrolyte concentrations. (a) CV cycle curves; (b) charge capacity

Fig. 5. Optical properties of WO₃ films after 6000 CV cycles under different electrolyte concentrations. (a) Transmittance curves; (b) modulation rate comparison at λ=550 nm

Fig. 6. Response time of WO₃ films after 6000 CV cycles under different electrolyte concentrations. (a) CA curves; (b) response time comparison; (c) injection current

Fig. 7. Electrochemical properties of WO₃ films after 6000 CV cycles under different electrolyte concentrations. (a) CV cycle curves; (b) charge capacity; (c) extracting and injecting charges and their ratios; (d) capacity loss

Fig. 8. CV curves of WO₃ films at different scan rates under different electrolyte concentrations. (a) 0.1 mol/L; (b) 0.5 mol/L; (c) 1.0 mol/L; (d) 2.0 mol/L; (e) ion diffusion coefficients

Fig. 9. Surface and cross-sectional morphologies of WO₃ films after 6000 CV cycles under different electrolyte concentrations. (a) , (b) 0.1 mol/L; (c) , (d) 0.5 mol/L; (e) , (f) 1.0 mol/L; (g), (h) 2.0 mol/L