High-Contrast Solid-State Electrochromic Devices of Viologen-Bridged Polysilsesquioxane Nanoparticles Fabricated by Layer-by-Layer Assembly
Applied Materials & Interfaces, 2009, 1, 83—89
The electrochromic properties of multilayer films fabricated with water-soluble silsesquioxane nanoparticles (NPs) incorporating viologen groups have been incorporated into solid-state devices. Electrochromic switching of the NPs in liquid electrolyte as well as in the solid state was evaluated by a kinetic study via measurement of the change in transmission (% T) at the maximum contrast. Cyclic voltammograms of the films exhibit a reversible reduction revealing good electrochromic stability, with a color change from orange to dark purple-blue at applied potentials ranging from -0.7 to -1.3 V. Cathodically coloring PXV NP solid-state devices exhibit a switching time of a few seconds between the purple-blue reduced state and the orange oxidized state, showing a contrast of 50% at 550 nm and a coloration efficiency of 205 cm2/C. Their solubility and fairly fast electrochromic switching (∼3 s) at low switching voltages (between 0 and 3.0 V), along with their stability under atmospheric conditions, make PXV NPs good candidates for electrochromic displays.
Changes in absorption (a and b) and appearance of fluorescence emission (c and d, λex = 351 nm) in 100 nm thin films before (a, c) and after (b, d) irradiation with <300 nm light for 3 min at room temperature.
A fluorescent anteater photo patterned by irradiation of photoresponsive hybrid films.
Transmission spectra from 0 to 3 V of a solidstate device fabricated by sandwiching two ITO electrodes coated with 40 bilayers of PXV NPs/ PAMPS and PANI/PAMPS. Inset: solid-state device changing color from yellow-green to dark purple-blue.