Abstract
The opto-electronic properties of native poly(p-phenylene vinylene) (PPV) were tuned by the confinement of the it-conjugation and the incorporation of a sulphur group as a spacer in order to obtain a blue-green emitting polymer (PPVS). The energy band gap of the PPVS thin film has been measured by UV-vis absorption spectroscopy and evaluated to 2.87 eV. Current-voltage characteristics and impedance spectroscopy measurements performed on sandwich structures [ITO/PPVS/Al] are used to elucidate the conduction mechanisms. The static electrical characterisations showed a space charge limited conduction (SCLC) and a conductivity with low power frequency behaviour characteristic of a hopping transport in disordered materials. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor R-P and capacitor C-P network in series with a resistor R. We extract numerical values of these parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterised by an exponential trap distribution. (C) 2011 Elsevier B.V. All rights reserved.