Red to Blue High Electrochromic Contrast and Rapid Switching Poly(3,4-ethylenedioxypyrrole)-Au/Ag Nanocomposite Devices for Smart Windows

Poly(3,4-ethylenedioxypyrrole) (PEDOP)-Ag and PEDOP-Au nanocomposite films have been synthesized for the first time by electropolymerization of the conducting-polymer precursor in a waterproof ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide, followed by Ag/Au nanoparticle incorporation. That the Ag/Au nanoparticles are not adventitious entities in the film is confirmed by a) X-ray photoelectron spectroscopy, which provides evidence of Ag/Au-PEDOP interactions through chemical shifts of the Ag/Au core levels and new signals due to Ag-N(H) and Au-N(H) components, and b) electron microscopy, which reveals Au nanoparticles with a face-centered-cubic crystalline structure associated with the amorphous polymer. Spectroelectrochemistry of electrochromic devices based on PEDOP-Au show a large coloring efficiency (eta(max)= 270 cm(2)C(-1), lambda = 458 nm) in the visible region, for an orange/red to blue reversible transition, followed by a second, remarkably high eta(max) of 490 cm(2)C(-1) (lambda = 1000 nm) in the near-infrared region as compared to the much lower values achieved for the neat PEDOP analogue. Electrochemical impedance spectroscopy studies reveal that the metal nanoparticles lower charge-transfer resistance and facilitate ion intercalation-deintercalation, which manifests in enhanced performance characteristics. In addition, significantly faster color-bleach kinetics (five times of that of neat PEDOP!) and a larger electrochemical ion insertion capacity unambiguously demonstrate the potential such conducting-polymer nanocomposites have for smart window applications.