Electrospun ion gel nanofibers for high-performance electrochromic devices with outstanding electrochromic switching and long-term stability

Here we present the enhanced electrochemical properties of ion gel nanofiber-based electrochromic devices (ECDs) prepared by electrospinning. The ECDs were fabricated by sandwiching prepared electrospun nanofiber webs between two transparent electrodes. The electrochromic behaviors of the ECDs were investigated using cyclic voltammetry, spectroelectrochemistry, and kinetic stability measurements. In order to determine the origin of the enhanced EC behaviors, the morphological structures of the nanofiber were examined by a scanning electron microscope, which showed that an ionic liquid (IL) region enclosed the pores between the nanofibers in the solid phase. The increased IL contents in the interstices of the nanofibers were noted, which would induce higher ionic mobility. Consequently, the fabricated nanofiber-based ECDs showed greatly enhanced device performance in terms of switching speed, cyclic stability, and coloration efficiency. Furthermore, flexible ECDs were fabricated by sandwiching the electrospun webs between two plastic electrodes consisting of silver nanowire/PEDOT:PSS hybrid electrodes. The fabricated device revealed a color switching over the large active area, with the transmittance changes maintained over repeated bending cycles. These nanofiber-based ECDs are evidence of a practical approach by which to realize large-area electrochromic devices with excellent chromatic switching and long-term cyclic stability, suitable both for rigid and flexible devices.