Charge percolation mechanism

Refs. [i] Chance RR, Boundreaux DS, Bredas J-L, Silbey R (1986) Solitons, polarons and bipolarons in conjugated polymers. In Skotheim TA (Ed) Handbook of conducting polymers, vol. 2, Marcel Dekker, p 825 [ii] Inzelt G (1994) Mechanism of charge transport in polymer-modified electrodes. In Bard AJ (Ed) Electroanalytical chemistry, vol. 18, Marcel Dekker [iii] Lyons MEG (1994) Charge percolation in electroactive polymers. In Lyons MEG (ed) Electroactive polymer electrochemistry, Parti, Plenum, New York, p 1... 

Figure 14-4. Dependence of the fraction of reacted redox center (R ) on its concentration in a matrix for various charge transfer mechanisms diffusion, hopping with bounded motion, and hopping without bounded motion (percolation).

Although metal hexacyanoferrates (HCFs) cannot be considered RPs, from both a structural and a compositional viewpoint, charge percolation occurs through electron-hopping mechanisms quite similar to those just described. For this reason, these pure inorganic materials are dealt with in the frame of this chapter. 

The electrochemical behavior of ZMEs is described in exhaustive reviews [17, 134], and the mechanisms involved in charge percolation processes inside ZMEs are also at the basis of the applications of these materials in electroanalysis and of the strategies followed to exploit their properties. The charge percolation process is... 

This model is formulated by assuming that the two fundamental steps in the charge percolation process occur in a sequential manner. However this mechanism implies that the system passes through two rather energetically unfavorable states bottom left and top right in Fig. 1.16). Hence it appears that an energetically more favorable situation involves a concerted pathway (the dotted path in Fig. 1.16). Saveant has modeled this situation in terms of Marcus theory. Equations 78 and 79 are still valid. However in this case the equation for the diffusion coefficient must be replaced by defined in Eqn. 91. 

In Section 2 we discussed the fundamental mechanisms of charge percolation in electroactive polymer films. Hence from a fundamental point of view, to quantify charge percolation fully in a polymer layer, we... 

It is not always recognized that potential sweep voltammetry can be used to obtain quantitative information on charge percolation in polymer films. We now briefly indicate how apparent charge transport diffusion coefficients can be extracted by analyzing such voltammetric parameters as peak current, peak width, and peak potential as a function of scan rate. This analysis is diffusional in concept and perhaps best applied to polymer materials where redox conduction is the predominant mechanism of charge transport. 

The room temperature conductivities of polycrystalline samples of [(PcMO)lv] (M = Si, Ge) for various stoichiometries are given in Table 15.1. The nature of the dopant (iodine, bromine, quinones, etc.) has no significant effect on the conductivities [125,128-130], In addition to the main charge transport mechanism via the phthalocyanine system, other mechanisms, e.g, percolation theory and fluctuation-induced carrier tunneling through potential barriers separating metal-like regions, have also been discussed [131]. 

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