Charge transport study of chemically synthesized polypyrroles soluble in organic solvents

Understanding the doping dependence of the conductivity of conjugated polymers: Dominant role of the increasing density of states and growing delocalization

“…At sufficiently low T, Mott's law (T)ϭ 0 exp͓Ϫ(T 0 /T) 1/4 ͔ for threedimensional VRH holds. 16 Such a T dependence of has been frequently reported in doped conjugated polymers, [5][6][7][8] and is suggestive of thermally activated tunneling of carriers between localized states in a constant density of states. As in other conjugated polymers, [2][3][4][5] seven orders of magnitude.…”

“…Although the fact has been demonstrated and discussed many times since, 1 the steeply nonlinear functional relation between dopant concentration and conductivity in the insulating state has not been consistently explained. [2][3][4][5] For the more frequently studied and equally steep temperature dependence of the conductivity, [5][6][7][8] various approaches exist, which have in common that some kind of phononassisted hopping between localized states allows the dc transport. In these models disorder, correlations and ͑bi͒polaron formation can play a role as well and often simplifying assumptions have been made about the shape of the density of states ͑DOS͒.…”

Characteristics of flexible electrode made on cellulose by soluble polypyrrole coating

“…It is also reported that dielectric constant of the organic solvents significantly influences the conductivity; the dielectric constant of the solvent is directly proportional to conductivity. 7 Figure 2(b) shows the SEM image of NSA-doped PPy–NMP solution. It is observed that the soluble PPy retained its granular structure with more uniform shape and size after dissolving in NMP.…”

“…This would improve inter-chain charge transport, attributes large conductivity. 7 The conductivity was then calculated using the following equation 8,9 where Δ I/ΔV denotes the slope of the current versus voltage curve, L the length (2 cm), w the width (1 cm) and d the thickness of the sample. Pristine cellulose exhibited an insulator behavior; on the other hand, electrical conductivity of the NSA-doped PPy–NMP-coated cellulose was found to be 3.41 × 10 −3 , 0.022 and 0.042 S/cm for one-, two- and three-layer coatings, respectively.…”