Poly(propylene glycol) Diacrylate Crosslinker in Gel Polymer Electrolytes for Glass‐based Electrochromic Devices

Electrochromic devices (ECDs) are promising as smart windows, as they provide dynamic control over light transmission and contribute to reducing energy costs in buildings. However, sluggish response times and low cycling stability highlight key barriers to their commercialization. One approach to tackle these is to optimize gel polymer electrolytes (GPEs) for ECDs, as they already balance high ionic conductivity and low risk of leakage. This study compares the GPE compositions with and without crosslinker poly(propylene glycol) diacrylate (PPGDA) in hybrid and inorganic ECDs. These include Fe(II) metal coordination polymer (Fe(II)-MCP) with Prussian blue (PB) and WO3 with NiOx. Some of the ECD performance parameters are not altered, like contrast ratio and coloration efficiencies, as they correspond to the electrochromic materials. By adding PPGDA to the GPE the charge density is lower for both cell types and the cyclability over 1000 switching cycles is demonstrated. Additionally, PPGDA reduces the bleaching time for the WO3/NiOx device, while the coloring time of the Fe(II)-MCP/PB devices slightly increases. These results show the benefits of the crosslinker PPGDA in a GPE on response time and cycling stability of two various ECDs.