Interchain charge mobility

Figure 10-2 7/t/e/chain charge mobility. Although the dopant counterion, ag., I (which also easts as I3" and Ij" ) has been omitted from these drawings, it may play a role in interchain transport. 

The TT-bonding leads to 7r-electron delocalization along the polymer chains and, thereby, to the possibility of charge carrier mobility, which is extended into three-dimensional transport by the interchain electron transfer interactions. In principle, broad Ti-electron bandwidths (often several eV) [10,11] can lead to relatively high carrier mobilities. 

Although the electrical conductivity is enhanced by the relatively high mobility associated with intra-chain transport, one must have the possibility of inter-chain charge transfer to avoid the localization inherent to systems with a one-dimensional electronic structure [237,238]. The electrical conductivity becomes three-dimensional (and thereby truly metallic) only if there is high probability that an electron will have diffused to a neighboring chain prior to traveling between defects on a single chain. For well-ordered crystalline material in which the chains have precise phase order, the interchain diffusion is a... 

This significant low-field conductivity demonstrates that conjugated polymers can be encapsulated in nanometer channels and still support mobile charge carriers. In contrast to the experiments with polypyrrole in zeolite Y and mordenite (see above), the channels in the MCM host provide more space and apparently allow some important interchain contact to occur. 

The mobility estimated from other measurements sometimes shows much higher values [see, e.g., [251] and references therein). This can either be due to wrong estimations or to a strong decrease of the mobility in field effect transistors due to interface states. The latter assumption is supported by the increase of the field effect mobility by using different insulators (compare Section 6.3). The mobility can further be increased by the electrochemical inclusion of Ag or Cu which probably create metallic bridges improving the interchain charge transfer rate [252,253]. 

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