Electro-synthesis, characterization and photoconducting performance of ITO/polybithiophene-MnO2 composite

Manganese dioxide is synthesized by reduction reaction of potassium permanganate with hydrogen peroxide. The as-synthesized α-MnO2 is characterized by powder X-ray diffraction and infrared spectroscopy. The MnO2 particles are used to prepare composite films containing polybithophene (PBTh) on indium tin oxide (ITO) glass substrates. The composite films ITO/PBTh-MnO2 are obtained by electro-polymerization of bithiophene in the presence the α-MnO2 particles dispersed in the electrolytic solution. The XRD and SEM analyses show that the α-MnO2 particles of size in the range 100-300 nm are incorporated in the polymer. The films are characterized by cyclic voltammetry impedance spectroscopy, UV-vis spectroscopy and scanning electron microscopy. As a result, the electrochemical gap and the optical gap are shifted by the incorporation of MnO2 from 2.15 eV for ITO/PBTh to 1.88 eV for ITO/PBTh-MnO2, while the electrical conductivity decreases from 195.35 S/cm for ITO/PBTh down to 0.047 S/cm for ITO/PBTh-MnO2 at the highest MnO2 investigated. The photo-electrochemical measurements also indicate that the ITO/PBTh-MnO2 films show a photocurrent that is three times higher than that of ITO/PBTh substrate to reach 20.6 μA cm−2, so that such a composite can be used as a new active material in solar cells.