Magnetoresistance in electrochemically deposited polybithiophene thin films

Magnetoresistance phenomenon on organic semiconductors has been studied mostly on spin-coated or vacuum thermal sublimated materials. In this work, electrochemistry is used as organic deposition technique. We report electrical measurements with an applied magnetic field on devices constructed in the sandwich structure indium tin oxide (ITO)/poly(bithiophene) (PBT)/aluminum (Al). The PBT polymer was electrochemically deposited on ITO. Hole mobility of 2.6 × 10−5 cm2/Vs was measured by impedance spectroscopy measurements, and thermally stimulated current measurements indicated two trapping states with activation energies around E 1–3 = 0.49 eV and E 4 = 0.51 eV. The interface ITO/PBT was characterized as a tunneling junction with ~0.9 eV energy barrier for hole injection from ITO. The highest magnetoresistance, ~0.6 %, was observed for a 273-nm PBT thickness, independent on direction between current and magnetic field.