IV. Two-dimensional variable-range hopping in planar conjugated macromolecules

Abstract

Abstract Electrical conductivity, thermopower and Hall effect measurements have been made on a series of polyacene quinone radical (PAQR) polymers as a function of temperature. The PAQR polymers, prepared by condensing pyrene with three different acidic compounds, are highty conjugated and show fairly high conductivities (in the range 10−4-10−3 Ω−1 cm−1 at room temperature). The thermopower is positive and increases slightly with increasing temperature. The Hall coefficient, measured on one sample, is negative and decreases with temperature; the Hall mobility is less activated than the conductivity and is of the order of 3 × 10−2 cm2 V−1 s−1 at room temperature. In order to alter the electrical properties by doping, the PAQR polymers were treated with iodine. This results in an increase of the conductivity, a sign reversal of the thermopower and a lowering of the Hall mobility. The conductivity and thermopower data seem to be explained in their general features by the two-dimensional variable-range hoppin...