Electrical transport properties of poly [2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] thin films doped with acridine orange dye

The electrical properties of poly[2-methoxy-5-(2'-ethyl hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) films were studied at different concentrations of acridine orange (AO) dye in the temperature range (293-416 K). MEH-PPV was dissolved in n-butyl acetate and was doped with different concentrations of AO dye solution. The MEH-PPV films were prepared by spin-coating technique with the speed of 1000 rpm. For conductivity measurements, Cu electrode contacts in planar configuration were made on the top surface of the film by RF sputtering. The DC conductivity and steady-state photoconductivity measurements were performed on these spin-coated thin films. It was observed that the doping of AO dye reduces the electrical resistivity as well as activation energies and enhances DC conductivity and photoconductivity. An increase in DC conductivity can be explained in terms of hopping conduction in the wide range of localised states. Photoconductivity measurements are useful in determining the nature of optical charge generation and transport in conjugated polymers. The value of To (measurement of disorderness) is in good agreement with the XRD spectra, which depicts the amorphous nature of the pure MEH-PPV film. Photocurrent dependence on incident radiation has also been observed which follows the power law (I-ph proportional to F-gamma). This dependence shows that the recombination with in the localised state is predominant. (c) 2007 Elsevier B.V. All rights reserved.