Thin and porous polymer membrane-based electrochromic devices

Abstract

An electrochromic (EC) device based on a thin and porous polymer membrane was newly fabricated for large-area applications such as smart windows. The pore structure of the poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) membrane was generated by extracting the pore generation material, dibutyl phthalate (DBP), from the cast film consisting of PVdF-HFP and DBP. The thickness of the porous polymer membrane was controlled to be very thin (approximately 30 μm), and the membrane was used to assemble WO₃/W-NiO EC devices with 1 M LiClO₄ in propylene carbonate as liquid electrolyte. Since the porous polymer membrane has a higher ionic conductivity than the non-porous one, the EC device with the porous polymer membrane showed a much higher current density in cyclic voltammetry even at a high scanning rate, faster color changing speed, and better stability after 500 cycles.