Percolation effect of V2O5 nanorod/graphene oxide nanocomposite films for stable fast-switching electrochromic performances

In the present study, V2O5 nanorod (VR)/graphene oxide (GO) nanocomposite films that can be used as an electrochromic (EC) material have been developed using the sol-gel spin-coating method. In order to optimize the nanocomposite effect of GO consisting of the VR films on EC performances, we controlled the volume percentage of GO compared to vanadium precursor to 0, 1, 2, and 3 vol%. With the increase of GO in VR films to 2 vol%, the resultant films exhibited a densely percolated structure, which was due to the nanocomposite effect of GO to generate the VR growth by an interaction with the oxygen-containing functional groups of GO. Due to the effect of optimized GO, the VR/GO nanocomposite films fabricated with 2 vol% GO revealed fast switching speeds (2.5 s for the bleaching speed and 1.4 s for the colouration speed). This was the result of an improved electrical conductivity and ion diffusion coefficient and high cycling retention of transmittance modulation (94.90% after 500 cycles) stemming from the remarkable electrochemical stability of the films as compared to those of bare VR films.