Electrochromic devices (ECDs) are devices that change their optical properties in response to a low applied voltage. These devices typically consist of an electrochromic layer, a transparent conducting substrate, and an electrolyte. The advancement in solid-state ECDs has been driven by the need for improved durability, optical performance, and energy efficiency. In this study, we investigate varying the temperature to the casting solution for polymethylmethacrylate (PMMA)-based electrolytes for solid-state ECDs with a structure of glass/ITO/WO₃/PMMA electrolyte/ITO/glass. The electrochromic layer, composed of WO₃, was deposited using the sol-gel method, while the electrolyte, comprising lithium perchlorate (LiClO₄) in propylene carbonate (PC) with PMMA, was prepared via solution casting. Various electrolyte samples were heated at different temperatures of 25, 40, 60, 80, and 100 °C to analyze the impact on the devices’ performance. Our findings indicate that the devices with electrolytes at 25 °C exhibited superior anodic and cathodic diffusion. An increase in heating temperature corresponded with an increase in switching time. Notably, the sample heated at higher temperatures (60, 80, and 100 °C) demonstrated exceptional cycle stability. Nevertheless, samples with higher temperatures displayed a decrease in optical modulation. Additionally, the 100 °C sample exhibited the highest coloration efficiency compared to other samples at lower temperatures. This research highlights the potential of varying the temperature of solution casting on PMMA-based electrolytes in optimizing the performance of solid-state ECDs, particularly regarding coloration efficiency and durability.

Electrochromic (EC) smart windows are a type of glass window that can change from transparent to darker colour shades when a small voltage is applied. Titanium dioxide (TiO2) can be utilised as an EC material for EC smart windows. Although the TiO2 sol-gel spin-coating method is commonly used, the effect of the number of TiO2 layers was not reported. Thus, this paper investigates the effect of the number of TiO2 layers. The increasing number of TiO2 film layers demonstrated a noticeable increase in the thin films ‘anodic and cathodic diffusion coefficient, particularly with 11 TiO2 layers. Additionally, the colouration and bleaching time was revealed to have a low correlation as the number of layers increased. Nonetheless, the lower number of TiO2 layers resulted in lower colouring transmittance. Comparatively, the colouration efficiency for all films did not exhibit any significant change. Hence this study on the effect of the TiO2 layering technique can open a new pathway in understanding the EC properties of TiO2-based EC devices.