Conducting doping with electron acceptors

Polyaromatic sodium lignosulfonate and sulfur lignin resin can be made conducting by doping. The conductivity increases by several decades through doping with electron acceptors and donors as shown in Table IV. 

As we can see from the Table all the three chains (and this is the case also for further two other polyacetylene and three polydiacetylene chains (7) which also have been calculated) have broad valence and conduction bands with widths between 4.4 and 6.5 eV-s. Comparing the band structure of the two polyacetylene chains we can find that the position of the bands and their widths is not very strongly influenced by the different geometries. This is again the case if we compare the here not described band structures of the further polyacetylene and polydiacetylene chains. On the other hand the position of the valence and conduction bands and the widths of the valence bands of the polydiacetylene chains is more different from those of the polyacetylene chains. To conclude we can say that due to the broad valence and conduction bands of these systems (which mean rather large hole and electron mobilities,respectively) one can expect that if doped with electron acceptors or donors these systems will become good conductors, which is, as it is experimentally estab-... 

POLYACETYLENE. A linear polymer of acetylene having alternate single and double bonds, developed in 1978. It is electrically conductive, but this property can be varied in either direction by appropriate doping either with electron acceptors (arsenic pentaflnoride or a halogen) or with electron donors (lithium, sodium). Thus, it can be made to have a wide range of conductivity from insulators to n- or >-type semiconductors to strongly conductive forms, Polyacetylene can be made in both cis and trans modifications in the form of fibers and thin films, the conductivity... 

Many other air-stable conducting polymers followed (Fig. 12.10) polypyrrole, polythiophene, polyaniline (which had been known since the nineteenth century as "aniline black"), and so on (Table 12.4). These polymers are semiconducting, not metallic, when "doped" with electron donors or acceptors the individual conjugated chains have finite length, so the conductivity is limited by chain-to-chain hopping. Also, if the individual strands exceed four or so oligomers, the conjugation tends to decrease, as the strand tends to adopt a screw-type distortion. The transport within each strand is attributed to polarons and bipolarons. 

The doped (CH), with electron acceptor or donor such as AsF5,12, or Na, shows electric conductivity of 101 103 S cm-1 (Shirakawa et al., 1977 Chiang et al., 1977, 1978) and, hence, the electromagnetic wave of the frequencies in the IR regime becomes unable to transmit the doped (CH), due to the skin effect (e.g., Slater and Frank, 1947). At a slight... 

The unique properties of polymers such as polyacetylene, whose backbones consist of an alternating succession of single and double bonds, and most of which show extraordinary electrical, optical and magnetic properties including electrical conductivity when "doped" with electron donors or acceptors [35], are also outside the scope of this work. Sophisticated quantum mechanical treatments are required to predict these properties of such polymers. 

Fermi energy. An alumlnum-PAN Schottky junction has been reported. ( ) Enhanced conductivity via doping with halogen electron acceptors has been shown.(13, 14) Doping with electron donors has not been reported. 

The electric conductivity of p-PODA at room temperature is 10 Scm This corresponds to common insulating polymers in the glassy state. However, above 440 K, ionic conduction is observed. " Electrically conductive PODAs can be obtained by doping with electron donors or electron acceptors. Some varieties of PODA are semiconductors and exhibit photoconductive properties. Therefore, they are used in electrical applications. PODA films exhibit exceptional gas separation properties. ... 

All teclmologically important properties of semiconductors are detennined by defect-associated energy levels in the gap. The conductivity of pure semiconductors varies as g expf-A CgT), where is the gap. In most semiconductors with practical applications, the size of the gap, E 1-2 eV, makes the thennal excitation of electrons across the gap a relatively unimportant process. The introduction of shallow states into the gap through doping, with either donors or acceptors, allows for large changes in conductivity (figure C2.16.1). The donor and acceptor levels are typically a few meV below the CB and a few tens of meV above the VB, respectively. The depth of these levels usually scales with the size of the gap (see below). 

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