The role of grain boundaries in the DC conductivity of p-sexiphenyl films

The DC conductivity of p-sexiphenyl films 0.2-2.5 mum thick deposited on glass substrates was investigated at temperatures between 4.2 and 300 K to evaluate role of the grain boundary interfaces in the transport properties. Molecular dynamics simulations and quantum chemical modelling of the experimentally observed conductivity have shown that there exist at least three different phases of the films effectively contributing to the observed features of the DC conductivity: conductivity caused by proper crystalline states, conductivity originating from amorphous-like intergrain region and conductivity caused by grain boundaries. A comparison of experimental data with those calculated theoretically shows that the main contribution to the observed DC conductivity is supplied by the boundary region between the crystalline grains and the amorphous-like background, even though this region occupies a relatively low proportion of the total volume.