Electrochemical Deposition of Fused Polydithieno[3,2-B:2ʹ,3ʹ-D]Thiophene Combining Higher-Lying Homo Level with High Electrical, Optical and Morphological Stability

Fused-thiophene based conjugated polymer has received significant importance due to their planar and rigid structure, enhancing the performance of electronic devices. We herein report the electrochemical synthesis of polydithieno[3,2-b:2ʹ,3ʹ-d]thiophene (PDTT) on different working electrodes (platinum, glassy carbon and ITO-coated glass) as well as on flexible ITO-coated PET electrode via both potentiodynamic and potentiostatic electropolymerization method. The chemical and physical properties of the obtained polymer PDTT were characterized by Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), UV-Vis-NIR spectrophotometer and field emission scanning electron microscopy (FESEM). The color of the film is red-orange in neutral state and transmission blue-grey in oxidized state. The electrochemical, optical and morphological stability of the electrodeposited polymer film was examined by CV, absorption spectra at different time intervals and FESEM images, respectively. The adherence property of electrodeposited polymer films was checked by ultrasonication test. The polymer film shows good optical stability on repeating chemical doping/dedoping process as well as repeated bending on a flexible substrate. The electrochromic behavior of the polymer film was investigated at three different wavelengths, and coloration efficiency of 156.5 cm2C-1 and optical contrast of 26.4 % were recorded at 478 nm. Density functional theory (DFT) calculations on PDTT and its monomer were carried out to understand the structure and energy levels, and compared with the experimental data.