Electropolymerization and electrochromic properties of poly(3- bromothiophene) films on a transparent nano-mesoporous TiO₂ surface

Poly(3-bromothiophene) (PBrT) film was electrochemically synthesized onto a nano- and meso-porous TiO₂ surface layered on indium tin oxide (ITO) conducting glass by galvanostatically anodic polymerization, and the electrochromism of PBrT polymer supported on the surface of TiO2(PBrT/TiO2) was thoroughly investigated. The morphology of TiO₂2 film was characterized by atomic force microscopy. The electrochromism of PBrT film was investigated by UV-Vis spectroscopy, chronoamperometry and chronoabsorptometry. The results indicated that the PBrT/TiO₂ revealed more excellent electrochromic properties than the PBrT deposited on ITO(PBrT/ITO). The PBrT/TiO₂ polymer displayed vivid color changes between bright red and deep blue in its fully reduced and oxidized states with chromatic contrast of 22% at 730 nm, coulombic efficiency of 70%, coloration efficiency of 191.3 cm²·C^-1 (reduced state) and 88.9 cm ²·C^-1 (oxidized state), and good optical memory in the reduced state (E = -0.2 V). Results implied that the PBrT/TiO₂ could be a commercially promising electrochromic material, which may make it incorporate into an electrochromic device.