Conjugated chemical doping

Preliminary measurements of electrical conductivity of the conjugated derivatives of PBTAB, PBTB and PTTB obtained by the above treatment with bromine vapor are poor semiconductors with a conductivity of the order 10 °S/cm which apparently is not due to doping. Subsequent electrochemical or chemical doping of these polymers lead to 4-6 orders of magnitude increase in conductivity. Ongoing studies of the electrical properties of these conjugated polymers with alternating aromatic/quinonoid units will be reported elsewhere. 

The synthesis and characterization of polyacetylene (PA) provided new incentive for understanding 7r-electronic spectra, electron-phonon interactions and electronic correlations[l, 2, 14]. The electrical conductivity of chemically doped PA rivals that of metals. Families in Fig. 2 such as polydiacetylenes (PDAs), poly thiophenes (PTs), cr-conjugated polysilane (PSs) and polyparaphenylene vinylene (PPVs), among... 

IRAV modes have been observed in many conjugated polymers and oligomers, introduced either by chemical doping and by photo-excitation. The IRAV modes accompany each polaron or bipolaron excitation. Typically, the IRAV modes are used as an identification mark for the nature of the excitation (whether charged or neutral). However, there is almost no attempt to quantify the mechanism of pinning. 

The general reaction describing chemical doping of conjugated polymers with FeCls can be expressed as follows ... 

Chemical doping The doping charge (electron or hole) on the conjugated molecules or polymers comes from another chemical species (atom or molecule). The chemical species become the counterions of the polarons created on the conjugated materials. 

Aniline was the first example of the conjugated polymers doped by proton, it can be chemically oxidized by ammonium peroxydisulfate (APS). PANI has the advantages of easy synthesis, low-cost, proton doping mechanism, and is controlled by both oxidation and protonation state. Polyanilines are commonly prepared by the chemical or electrochemical oxidative potymerization of the respective monomers in acidic solution. But, other potymerization techniques have also been developed, including ... 

Frohne et al. varied the work function of the hole contact Pedot -PSS by ex situ adjusting its work function by controlled chemical doping [127]. They found that the Vqc directly scales with the work function difference of the PEDOT-PSS and the Al contact used. Interestingly, the reversed sign when the work function of the PEDOT-PSS was lower than the LUMO of PCBM, which further suggests the pinning of the top electrode work function. It also demonstrates that the hole contacts is not pinned to any of the electronic levels of the conjugated polymer or PCBM. 

Polyacetylene, a one-dimensional, conjugated polymer represented as (CH) exhibits electrical conduction upon chemical doping with an electron acceptor or donor [1,2]. The chemical doping transforms the polyacetylene from insulator or semiconductor to conductor. Ordinary polyacetylene film is composed of fibrils that are bundles of polyene chains. Because the fibrils are randomly oriented, the inherent electrical conductivity of the polyacetylene chain is depressed owing to fibril contact resistance. This makes it difficult for polyacetylene to become a complete one-dimensional conductor at the macroscopic level. Today, the primary concern is how to align the fibrils of polyacetylene film in order to achieve higher electrical conductivity. 

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