Polyvinyl butyral-based gel polymer electrolyte films for solid-state laminated electrochromic devices

Polyvinyl butyral-based gel polymer electrolyte films (PVB-based GPEFs) were prepared by casting method. The surface morphology and ionic conductivity of the PVB-based GPEFs were measured; cyclic voltammetry behavior, optical properties, and coloration efficiency of the devices were investigated. The SEM shows amorphous polymer matrix with interval and micropores among the molecule chains. With different volume of ionic liquid, the ionic conductivity of electrolyte films increased up to 4.0 × 10−-5 and 6.2 × 10−5 S/cm at 25 and 50 °C, respectively. Electrochromic devices (ECDs) with glass/ITO/WO3/PVB-based GPEF/Ni1-xO/ITO/glass configuration were prepared following the technology of laminated safety glass. The best device provided excellent electrochromic performances with high optical modulation of 65.8% at 550 nm, coloration efficiency of 175.34 cm2/C, and long-term stability. In addition, small color fading of 4.8% was observed under self-discharging conditions for 16 h, proving that the PVB-based ECD possesses sufficient memory effect as smart window.