Charge carrier migration

Addition of water increases the vertical distance between the charge carriers migrating in different horizontal levels so that they do hinder each other less, but it does not change their numbers, the forces of electric field driving them or the distances covered by them. 

In many perovskites, the distortion may be considerable, as with the Jahn-Teller effect or the influence of lone pair electrons. In such cases the distortion may prevent any charge carrier migration at all, and semiconducting behaviour is suppressed. Changing the degree of distortion by substitution will often reverse this. 

Both charge carriers migrate rapidly [16,17] to the surface ( see Fig.l) where they are ultimately trapped by intrinsic sub-surface energy traps (Ti -0 "-Ti ) for the hole and by surface traps (-Ti -) for the electrons (eqs.3,4) [18], and/or by extrinsic surface traps via interfacial electron transfer with adsorbed electron donors (Red2 ads) acceptors (Oxj ds) respectively (eqs. 5,6). 

When a polymer of (Xe > o-jon, such as polypyrrole in the oxidized state, is subjected to changes of the applied electrode potential, during the transient state electric fields develop in the polymer matrix and then disappear as electronic and ionic charge carriers migrate to new equilibrium positions [19,27,31,184]. The analyses may be based on the concepts derived for redox polymers under the condition that the hopping mobility of the electrons exceeds the counterion mobility. It has been shown [31] that in this case the system behavior is again diffusiona in character. The coated electrode behaves like a porous metal electrode with pores of limited depth. Numerous experimental reports on this behavior of conducting polymers have appeared in the literature the first was probably that of Bull et al. in 1982 [214]. 

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