Models of Charge Transport in Conducting Polymers

As discussed in previous sections, the mechanisms for the formation of metallic state and charge conduction in conducting polymers have been the subject of intensive study since the occurrence of an insulator to metal transition was reported upon doping. It is proposed that non linear defects such as polarons, solitons and bipolarons have a major role in these systems [36, 95-97]. In earlier synthesised conducting polymers, inhomogeneities often dominated the transport properties, and metallic island models were proposed to 

Similar to Kivelson s model. Chance and co-workers proposed interchain hopping for spinless conductivity in doped polyacetylene, doped poly(p-phenylene) and other doped polymers [102]. The mechanism accounts for the observed dopant concentration dependence of the conductivity in rans-polyacetylene and the observation of anomalously 

Kivelson and Heeger carried out a detailed study on the intrinsic conductivity of conducting polymers [77]. They described the expression for the conductivity as  

When the concentration of chain interruptions is sufficiently high such that the left hand side of equation 1.3 is small, then the wave function will be localised. The possible limits for the conductivity arise from the chain interruptions and/or phonon scattering. All the above factors suggest that in high-quality conducting polymers the electronic mean free path could be much larger than the structural coherence length and real metallic features could be observed. 

More recently, Samukhin and co-workers proposed [99] a q-lD fractals model in order to explain the experimental data obtained for poorly conducting polymers. It is found that at low temperatures, the VRH conductivity obeys a q-lD Mott s law, exp-fT /T), but 

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