Designed growth of hollow WO₃/PEDOT bilayer hybrid nanosphere arrays film with superior electrochromic and capacitive performance

In this work, hollow WO₃/poly(3, 4-ethylenedioxythiophene) (PEDOT) bilayer hybrid nanosphere arrays film was constructed by template-assisted magnetron sputtering combined with electrochemical deposition. The hollow nanosphere arrays could provide large contact area with electrolyte to benefit ion exchange. The prepared WO₃ layer was responsible for offering a lot of ions binding sites due to the large capacity of amorphous WO₃ for small ions, and the PEDOT layer was prepared to construct a unique conductive network which could effectively facilitate electron transportation and connect separated color centers. The obtained hollow hybrid nanosphere film exhibits outstanding electrochromic performance with high contrast (77.4% at 633 nm), fast response speed (3.2 s for coloring and 4.2 s for bleaching), good cycling stability (lose 14.5% optical modulation after 2000 cycles) and decent coloring efficiency (116.2 cm²·C⁻¹) at low colored/bleached potentials (−1.0/1.0 V). The hollow hybrid nanospheres also display high areal capacitance (54.6 mF/cm²), superior rate capability and cyclic stability (areal capacitance remains 79.6% after 2000 cycles).