Organic transistors and circuits are technologically interesting because they have potential to serve in inexpensive and flexible electronic circuits. Major applications include radio frequency identification tags and flexible display backplanes. These circuits can be potentially fabricated by simple printing methods, not requiring the demanding environment needed for silicon based circuitry. This paper reviews the principles of transistors and discusses the issues most important to organic transistors. It also covers the fabrication and properties of n-channel devices as well as ambipolar transistors.
"Dynamic increase of importance of organic materials in electronics  , photonics   and in similar branches of science had been observed since Hideki Shirakawa, Alan G. MacDiarmid and Alan J. Heeger had discovered accidentally the phenomenon of conduction of electric current in iodine doped polyacetylene   . This event opened a new chapter in the field of polymer science, allowing to improve (opto)electronic devices like solar cells  , light-emitting diodes  , filed effect transistors    and others  . "
[Show abstract][Hide abstract] ABSTRACT: Arylene diimide derivatives with imine linkages, that is, azomethinenaphthaldiimides end-capped with pyridine, thiophene, bithiophene, and (ethylenedioxy)-thiophene units and corresponding polymers with thiophene and bithiophene structure as charge-transport compounds were investigated. All compounds along with polymers form alternated electron-accepting (A)–electron-donating (D) systems, except of one contains the pyridine structure, which constitutes an A–D–A–D–A molecule. The effect of end-capping structure group on the spectroelectrochemical properties was studied. All compounds were electrochemically active and undergo reversible reduction and irreversible oxidation. They exhibited a low electrochemically (CV) calculated energy band gap (Eg), ranging from 1.09 to 1.78 eV. The lowest one was found for compound with (ethylenedioxy)-thiophene structure. Moreover, the attempt of electrochemical polymerization of azomethinenaphthaldiimides was undertaken. The changes in UV–Vis spectra recorded during electrochemical oxidation and reduction were observed. Results indicate the lack of interaction between imide groups and end-capping groups. In order to analyze the structure of charged forms created during electrochemical reduction, the EPR spectroelectrochemical measurements were performed.
"Ambipolar organic semiconductors capable of both efficient electron and hole transport are essential for the development of next generation opto-electronic devices, such as organic light-emitting transistors (OLETs)     , complementary metal-oxide semiconductor (CMOS) circuits   and sensors . "
[Show abstract][Hide abstract] ABSTRACT: Indigoids have received much attention as the candidates of sustainable ambipolar organic semiconductor. However, the low charge carrier mobilities extremely limit their practical applications. Therefore, in-depth understanding of their electronic-structure properties and rational molecular modifications are urgently required. Here, we propose a promising strategy to design ambipolar organic semiconductors based on indigo fragments. Moreover, we predicted the organic crystal structures by evolutionary algorithm combined with DFT-D method. Charge transport properties have been significantly improved for the designed molecules, such as narrower energy gaps, higher electron affinity, larger transfer inte-grals as well as much smaller reorganization energies for hole and electron. Thusly, remarkable ambipolar charge transport behavior has been predicted, for example, the charge carrier mobilities are up to h /l e = 7.71/5.42 cm2V-1s-1 for NN-indigo-6,6 0-2CN and l h /l e = 5.15/2.13 cm2V-1s-1 for C 9-NN-indigo-6,6 0-2CN respectively.
"However, one would expect a transport anisotropy in all cases, with charge transport favorably occurring along the p–p stacking direction, i.e., perpendicular to the H-bonding direction . Thus orientation of the p–p stacking parallel to the gate dielectric is critical for optimal transport in transistors  . It was reported that hydrophobic substrates are necessary to ensure such a stacking direction, as the hydrophobic van der Waals contacts of the H-bonded pigment molecules favorably interact with such surfaces. "
[Show abstract][Hide abstract] ABSTRACT: Diketopyrrolopyrroles (DPPs) have recently gained attention as building-blocks for organic semiconducting polymers and small molecules, however the semiconducting properties of their hydrogen-bonded (H-bonded) pigment forms have not been explored. Herein we report on the performance of three archetypical H-bonded DPP pigments, which show ambipolar carrier mobilities in the range 0.01-0.06 cm(2)/V s in organic field-effect transistors. Their semiconducting properties are correlated with crystal structure, where an H-bonded crystal lattice supports close and relatively cofacial π-π stacking. To better understand transport in these systems, density functional theory calculations were carried out, indicating theoretical maximum ambipolar mobility values of ∼0.3 cm(2)/V s. Based on these experimental and theoretical results, H-bonded DPPs represent a viable alternative to more established DPP-containing polymers and small molecules where H-bonding is blocked by N-alkylation.
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