Conducting polymers electrical transport properties

The optical properties of (CH) are of interest, since these directly give information about the band gap and/or the levels in the midgap, which is considered to be closely related with the electric transport property. Currently available experimental data on the photoabsorption of (CH), polymers are listed in Table IV. It seems to be reasonable to regard these absorption onsets as the it - tt interband transition energy from the HO to the LU band, that is, the band gap between the valence and the conduction bands in the sense of the one-electron approximation based on the one-dimensional Peierls transition mentioned in the Section II,A. 

In summary, CPs offer numerous advantages over inorganic semiconductors for thermoelectric applications because of their unique properties. However, the poor electrical transport properties have impeded their practical application as TE materials in the past. Recent studies indicate that incorporating the inorganic nanoparticle into polymer matrix is an effective way to improve the electrical transport properties of CPs, including electrical conductivity and Seebeck coefficient, while keep the thermal conductivity at low level simultaneously. Consequently, the power factors of most CP-based nanocomposites are about 2 3 orders of magnitude higher than those of conventional pure CPs and the maximum ZT value is up to 0.1 at present. 

In the past three decades, several types of r-electron systems have shown very interesting features in electrical transport properties [1-4]. Charge-transfer complexes, intercalated graphite, conjugated polymers, carbon-60, carbon nanotubes, etc., are some of the well-known r-electron systems. Polymeric materials were considered as insulators before the discovery of metallic poly(sulfur nitride), [SN],, and the enhancement of conductivity in doped poly acetylene, (CH),, by several orders of magnitude [4, 5]. 

This brief overview of the electrical transport properties in doped conducting polymers highlights the following points ... 

FIGURE 16.4 I-V characteristics of iodine doped PA nanofiber. Znsef shows scanning force microscope image of PA nanofiber on top of Pt electrodes (with 100 nm separation). Typical diameter of PA nanofiber is 16-20 mn (From Park, J.G., et al. Synth. Met., 119, 53, 2001 and Park, J.G., Electrical transport properties of conducting polymer nanostructures Polyacetylene nanofiber, polypyrrole nanotube/nanowire, Ph.D. thesis, Seoul National University, Seoul, 2003.). 

Park, J.G. 2003. Electrical transport properties of conducting polymer nanostructures Polyacetylene nanofiber, polypyrrole nanotube/nanowire. Ph.D. thesis, Seoul National University, Seoul. 

This article addresses the synthesis, properties, and appHcations of redox dopable electronically conducting polymers and presents an overview of the field, drawing on specific examples to illustrate general concepts. There have been a number of excellent review articles (1—13). Metal particle-filled polymers, where electrical conductivity is the result of percolation of conducting filler particles in an insulating matrix (14) and ionically conducting polymers, where charge-transport is the result of the motion of ions and is thus a problem of mass transport (15), are not discussed. 

Nalwa HS, "Handbook of Organic Conductive Molecules and Polymers", Vol. 1, "Charge-Transfer Salts, Fullerenes and Photoconductors" Vol. 2, "Conductive Polymers Synthesis and Electrical Properties" Vol. 3, "Conductive Polymers Spectroscopy, Photo-Physics and Applications" Vol. 4, "Conductive Polymers Transport and Physical Properties", Wiley, Chichester, 1997. 

We start our discussion with simple concepts from the band theory for solids, discuss what can break the symmetry of one-dimensional systems, introduce electrical conductivity and superconductivity, present the Mulliken charge transfer theory for solution complexes and its extension to solids, then discuss briefly the simple tt electron theory for long polyenes. Other articles in this volume review the detailed interplay between structure and electronic properties of conductors and superconductors [206], and electrical transport in conducting polymers [207],... 

---