Electrochromic response of nanostructured poly(3,4-ethylenedioxythiophene) films grown in an aqueous micellar solution

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been electropolymerized from an aqueous micellar solution encompassing the monomer (EDOT) and the moieties sodium dodecyl sulfate (SDS) and lithium triflate. The presence of these anionic dopants in the polymer matrix and a doping level of 0.26 have been confirmed by X-ray photoemission and electron paramagnetic resonance (EPR) spectroscopy. The hydrophobic micellar core encompassing the monomer orchestrates the growth of a uniform homogeneous polymer deposit as electron microscopy and atomic force microscopy studies reveal the film to be composed of a continuous interlinked network of quasi-spherical grains (50–150 nm in dimensions) and pores alongwith a low surface roughness. The film exhibits a large coloration efficiency of 153 cm² · C⁻¹ and a transmission modulation of 62% (λ = 632.8 nm), which are manifestations of the open ion-permeable morphology. The Q_{(inserted/extracted)} ratio ranges between 1.2 and 1.4 when cycled back and forth between the clear and blue states 2 500 times, thereby affirming the suitability of these films for practical electrochromic smart windows.