Electrochemical, optical and morphological properties of poly (N-vinylcarbazole/TiO 2 ) and (N-vinylcarbazole/aniline)/TiO 2 copolymer prepared by electrochemical polymerization

Poly (N-vinylcarbazole) (PVK) and a new copolymer, PVK/polyaniline (PANI), have been successfully prepared by electrochemical polymerization of N-vinylcarbazole (NVK) and NVK/aniline from acetonitrile medium and LiClO 4 supporting electrolyte. Composite thin films were studied by cyclic voltammetry (CV) in LiClO 4 /acetonitrile solutions on an indium tin oxide (ITO) electrode. The influences of concentration of titanium dioxide (TiO 2 ) on the electrochemical properties of these composite materials were also investigated. The results of scanning electron microscopy (SEM) confirm the presence of TiO 2 in the composite, which consequently modifies the morphology of the film significantly. Topographical analysis has shown that TiO 2 nanoparticles (NPs) affect the morphology of thin films (roughness). The analysis of the voltammograms of PVK and of (PVK+PANI) before and after the addition of TiO 2 at different concentrations shows a redox couple which was not observed in the absence of TiO 2 . The impedance spectroscopy study shows that the resistance of the PVK and (PVK+PANI) films decreases with increasing of TiO 2 concentration, and this in turn contributes to a good conductivity of the film. The optical characterization of the composites has been carried out by UV-Vis absorption and photoluminescence (PL) spectroscopy and it was noted that the samples (PVK+10 −2 TiO 2 ) exhibited high transmittance (83%) in the visible region and a low gap value (2.69 eV) which confirms that this material can be used in a photovoltaic cell. This is explained by the introduction of the donor levels in the band gap of PVK by the TiO 2 , due to an effective doping.