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ABSTRACT Owing to changes in their chemistry and structure, polymers can be fabricated to demonstrate vastly different electrical conductivities over many orders of magnitude. At the high end of conductivity is the class of conducting polymers, which are ideal candidates for many applications in low-cost electronics. Here, we report the influence of the nature of the doping anion at high doping levels within the semi-metallic conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on its electronic transport properties. Hall effect measurements on a variety of PEDOT samples show that the choice of doping anion can lead to an order of magnitude enhancement in the charge carrier mobility > 3 cm2/Vs at conductivities approaching 3000 S/cm under ambient conditions. Grazing Incidence Wide Angle X-ray Scattering, Density Functional Theory calculations, and Molecular Dynamics simulations indicate that the chosen doping anion modifies the way PEDOT chains stack together. This link between structure and specific anion doping at high doping levels has ramifications for the fabrication of conducting polymer-based devices. © 2017 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 97-104 [ABSTRACT FROM AUTHOR]

The power conversion efficiency of solar cells based on a conjugated polymer (donor) and a fullerene derivative (acceptor) is very sensitive to the morphology of the active layer. One detrimental feature, which is often encountered in non-optimal morphologies, is the occurrence of fullerene blobs in a finely mixed matrix containing both donor and acceptor material. Here, the effects of such fullerene blobs are studied in detail with a three-dimensional drift-diffusion model. It includes the effects of exciton diffusion and quenching; space-charge; recombination, generation, drift and diffusion of charge carriers; and the injection/extraction of carriers at the contacts. The influence of blob size and shape, and matrix composition are quantified. The latter has the strongest effect on the overall efficiency, as most of the current is transported through the mixed phase. The total current flowing out of the solar cell can be split up in a part which comes from the interfacial region between the acceptor phase and the mixed phase, and a part that stems from the mixed phase itself. Depending on the bias voltage and the morphology, one or the other contribution is dominant. Finally, it is shown how both contributions can be computed with a simple one-dimensional drift-diffusion simulator. [ABSTRACT FROM AUTHOR]

Current organic semiconductors for organic photovoltaics (OPV) have relative dielectric constants (relative permittivities, εr) in the range of 2-4. As a consequence, Coulombically bound electron-hole pairs (excitons) are produced upon absorption of light, giving rise to limited power conversion efficiencies. We introduce a strategy to enhance εr of well-known donors and acceptors without breaking conjugation, degrading charge carrier mobility or altering the transport gap. The ability of ethylene glycol (EG) repeating units to rapidly reorient their dipoles with the charge redistributions in the environment was proven via density functional theory (DFT) calculations. Fullerene derivatives functionalized with triethylene glycol side chains were studied for the enhancement of εr together with poly( p-phenylene vinylene) and diketopyrrolopyrrole based polymers functionalized with similar side chains. The polymers showed a doubling of εr with respect to their reference polymers in identical backbone. Fullerene derivatives presented enhancements up to 6 compared with phenyl-C61-butyric acid methyl ester (PCBM) as the reference. Importantly, the applied modifications did not affect the mobility of electrons and holes and provided excellent solubility in common organic solvents. [ABSTRACT FROM AUTHOR]

The charge transport characteristics of organic semiconductors are one of the key attributes that impacts the performance of organic electronic and optoelectronic devices in which they are utilized. For improved performance in organic photovoltaic cells, light-emitting diodes, and field-effect transistors (FETs), efficient transport of the charge carriers within the organic semiconductor is especially critical. Characterization of charge transport in these organic semiconductors is important both from scientific and technological perspectives. In this review, we shall mainly discuss the techniques for measuring the charge carrier mobility and not the theoretical underpinnings of the mechanism of charge transport. Mobility measurements in organic semiconductors and particularly in conjugated polymers, using space-charge-limited current, time of flight, carrier extraction by linearly increasing voltage, double injection, FETs, and impedance spectroscopy are discussed. The relative merits, as well as limitations for each of these techniques are reviewed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]