A complementary electrochromic device based on W18O49 nanowire arrays and Prussian blue thin films

Abstract

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 (t_c) and 3.1 s for bleaching (t_b), 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.