A complementary electrochromic device based on W18O49 nanowire arrays and Prussian blue thin films
Tungsten oxides (W18O49) nanowire arrays as effective electrochromic working electrodes were fabricated on seed-free FTO glasses through a facile solvothermal process. XRD, FESEM and TEM were used to characterize the phase, morphology and nanostructure. Uniform monoclinic W18O49 nanowire arrays can be obtained at 180 °C for 5 h. In the assembled electrochromic device the W18O49 nanowire array films show a fast response and switching time, extracted for a 50% transmittance change of 10.8 s for coloration (tc) and 3.1 s for bleaching (tb), which surpass current traditional devices using monoclinic tungsten oxide (WO3) as the electrochromic material. The reasons can be attributed to their large specific surface area, special tunnel structure and non-stoichiometry characteristics. A complementary electrochromic device combining the W18O49 nanowire arrays with Prussian blue film shows a higher optical contrast (59.05% at 632.8 nm) and a faster switching response with a coloration time of 6.9 s and a bleaching time of 1.2 s, superior to the single layer W18O49 nanowire device. The complementary device with excellent electrochromic performance demonstrates a great potential for practical application.