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This paper deals with the electrochemically induced charge injection in the conductive polymer (CP), exemplified by well examined archetypal CP—poly(3-hexylthiophene-2,5-diyl). The polar solvent of acetonitrile with salt tetrabutylammonium hexafluorophosphate was used to transport electrons in the electrolyte. The decisive mechanism is the recombination current at the electrolyte/CP interface taking place at the Fermi energy of CP, whose energy position is determined by the externally applied voltage. The corresponding mechanism of the charge carrier transport in the polymer bulk is the space-charge limited current (SCLC) by holes or electrons (or more precisely positive and negative polarons) at the respective transport paths of HOMO and LUMO bands. The charge transport mechanisms and the occupation statistics are the basis of the energy-resolved electrochemical impedance spectroscopy for the mapping of the density of electronic states of conductive organic semiconductors [F. Schauer, V. Nádaždy, and K. Gmucová, J. Appl. Phys. 123, 161590 (2018)]. From the application point of view, the major message of the paper is that it is possible to pass high current densities of the order of 0.1 A cm−2 via electrochemical systems with the CP, induced by means of doping processes of both CP surface and its bulk, leading to the charge injection and SCLC in CP. [ABSTRACT FROM AUTHOR]

There is potential in applying conjugated polymers in novel organic optoelectronic devices, where a comprehensive understanding of the fundamental processes and energetics involved during transport and recombination is still lacking, limiting further device optimization. The electronic transport modeling and its optimization need the energy distribution of transport and defect states, expressed by the energy distribution of the Density of States (DOS) function, as input/comparative parameters. We present the Energy Resolved-Electrochemical Impedance Spectroscopy (ER-EIS) method for the study of transport and defect electronic states in organic materials. The method allows mapping over unprecedentedly wide energy and DOS ranges. The ER-EIS spectroscopic method is based on the small signal interaction between the surface of the organic film and the liquid electrolyte containing reduction-oxidation (redox) species, which is similar to the extraction of an electron by an acceptor and capture of an electron by a donor at a semiconductor surface. The desired DOS of electronic transport and defect states can be derived directly from the measured redox response signal to the small voltage perturbation at the instantaneous position of the Fermi energy, given by the externally applied voltage. The theory of the ER-EIS method and conditions for its validity for solid polymers are presented in detail. We choose four case studies on poly(3-hexylthiophene-2,5-diyl) and poly[methyl(phenyl)silane] to show the possibilities of the method to investigate the electronic structure expressed by DOS of polymers with a high resolution of about 6 orders of magnitude and in a wide energy range of 6 eV. [ABSTRACT FROM AUTHOR]

A study was conducted to derive some insights into the microphysics of field effect transistors. An iterative scheme was used to model the space charge, trap occupation and current distribution of the structure of the typical, thin, organic or semiorganic amorphous semiconductor-based field effect transistor. Current on the gate voltage and activation energy of the field effect on the gate voltage was calculated. Results of the study are presented.