Electrochromic properties of WO3 films based on lithium iodide and lithium perchlorate polymer electrolyte

Abstract Electrochromic (EC) window is a novel intelligent window technology which functions by switching between transparent and opaque states thereby allowing the energy saving, healthy and comfort living environment within residential and commercial building premises. In general, each layer is important in ensuring the smooth operation of an EC window. In particular, the electrolyte layer is one of the more important layers due to the fact that its material composition will directly impact the operation of the EC window. In this work, WO3 films were fabricated using sol-gel spin-coated technique on indium tin oxide (ITO) coated glasses. Lithium iodide in polyethylene glycol (PEG:LiI) and lithium perchlorate in propylene carbonate (PC:LiClO4) were used as polymer electrolytes. Subsequently, the EC performance of WO3 films using the mentioned polymer electrolytes were examined by cyclic voltammetry (CV) and chronoamperometry (CA) techniques. The optical properties of the WO3 films were measured by using the ultraviolet-visible (UV–vis) spectrophotometer. The electrolytes based on PEG:LiI and PC:LiClO4 have been the mainstream electrolytes with variant EC performance, and yet, the direct comparison of these polymers electrolytes were not explored. Therefore, the current work here is important to outline the characteristics of these electrolytes in determining the EC performance on WO3 films.