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Conducting and semiconducting polymers are important materials in the development of printed, flexible, large-area electronics such as flat-panel displays and photovoltaic cells. There has been rapid progress in developing conjugated polymers with high transport mobility required for high-performance field-effect transistors (FETs), beginning with mobilities around 10(-4) cm(2) V(-1) s(-1) to a recent report of 1 cm(2) V(-1) s(-1) for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). Here, the electrical properties of PBTTT are studied at high charge densities both as the semiconductor layer in FETs and in electrochemically doped films to determine the transport mechanism. We show that data obtained using a wide range of parameters (temperature, gate-induced carrier density, source-drain voltage and doping level) scale onto the universal curve predicted for transport in the Luttinger liquid description of the one-dimensional 'metal'.

This article presents an overview of the charge transport phenomenon in semiconducting polymer materials. In these disordered systems both intrinsic and extrinsic parameters play significant roles. In general, π‐electron delocalization, interchain interaction, band gap, carrier density, extent of disorder, morphology and processing of materials determine the electrical and optical properties. The chemical structure, especially the role of side groups, is quite important in both physical and processing properties. The nature of charge carriers and their role in charge transport depend on the structure and morphology of the system. Hence in several semiconducting polymer devices, the correlations among structure, morphology and transport are rather strong. The dependence of carrier mobility on temperature and electric field needs to be understood in the framework of competing models based on carrier hopping, trapping/detrapping and tunneling. Exactly what determines the dispersive/nondispersive, polaronic and correlative transport regimes is yet to be quantified. An understanding of the carrier mobility in semiconducting polymers is necessary to optimize the performance of polymeric electronic devices. Copyright © 2006 Society of Chemical Industry

By controlling the extent of disorder through electrochemical synthesis at reduced temperatures, conducting polypyrrole (PPy) can be obtained in the metallic regime, in the insulating regime, and in the critical regime of the disorder-induced metal-insulator (M-I) transition. We present the results of reflectance measurements (0.002 -6 eV) of PPy carried out at room temperature on the metallic side and on the insulating side of the M-I transition. While the reflectance spectra obtained from samples on both sides of the M-I transition exhibit spectral features expected for a partially filled conduction band, the electronic states near the Fermi energy (EF) are different in the two regimes. The data obtained from metallic samples indicate delocalized electronic wave functions in the conduction band, whereas the spectral features which characterize the insulating regime indicate that the states near E+ are localized. Consistent with theoretical predictions for the metallic and insulating regimes, the optical conductivity o. (co) and the real part of the dielectric function E&(co) each show different frequency dependences in the far infrared. In the metallic regime o(co)~c o' for Am&600 cm ' and c&(co) ( &0) increases rapidly as co~0, as described by the "localization-modified Drude model, " leading to the conclusion that metallic polypyrrole is a disordered meta/ near the M-I transition. In contrast, the insulating regime is characterized as a Fermi glass as confirmed by o (co)~co for A~& 600 cm