Background: Since the last decade, there has been much interest in solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications.

Methods: In this work, tungsten oxide (WO₃) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE) respectively, using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO₃ films as working electrode.

Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation.

Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analyzed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

Experimental data was collected based on transmittance using UV-Vis spectrophotometer, cyclic voltammetry and chronoamperometry using potentiostat/galvanostat measurement methods. Measured data are extracted and further analysed through the relevant equations.