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

Abstract

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 LiClO4 supporting electrolyte. Composite thin films were studied by cyclic voltammetry (CV) in LiClO4/acetonitrile solutions on an indium tin oxide (ITO) electrode. The influences of concentration of titanium dioxide (TiO2) on the electrochemical properties of these composite materials were also investigated. The results of scanning electron microscopy (SEM) confirm the presence of TiO2 in the composite, which consequently modifies the morphology of the film significantly. Topographical analysis has shown that TiO2 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 TiO2 at different concentrations shows a redox couple which was not observed in the absence of TiO2. The impedance spectroscopy study shows that the resistance of the PVK and (PVK+PANI) films decreases with increasing of TiO2 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 TiO2) 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 TiO2, due to an effective doping