Electrochemical, optical and electrochromic properties of fused polydithienothiophene: A stable material with reversible doping

Fused-thiophene-based conjugated materials have received great importance due to their rigid and planar structure, enhancing the performance of electronic devices. We herein report the electrochemical synthesis of polydithieno[3,2-b:2′,3′- d ]thiophene (PDTT) on different working electrodes (platinum, glassy carbon and ITO-coated glass) as well as on flexible ITO-coated PET electrode. We used both potentiodynamic and potentiostatic electropolymerization methods for the deposition of polymer films using TBAClO ₄ /MeCN electrolyte-solvent system. The chemical and physical properties of the obtained polymer PDTT were characterized by FTIR, cyclic voltammetry, electrochemical impedance spectroscopy, UV–vis–NIR spectrophotometer and FESEM. The color of the film was red-orange in neutral form and transmission blue-grey in oxidized form. We explored the properties of PDTT in terms of electrochemical, optical and morphological stability, adhesion and chemical doping-dedoping. Further, the electrochromic behavior of the polymer films is presented at different wavelengths, and the coloration efficiency of 156.5 cm ²C ⁻¹ and the maximum optical contrast of 26.4 % were recorded in the visible region. Finally, density functional theory (DFT) calculations on PDTT and its monomer were performed to understand the structure and energy levels and further compared with the experimental results.