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Pentacene films deposited with molecular beam deposition have been fabricated and characterized with respect to structure and morphology using x-ray diffraction and scanning electron microscopy. Metal-insulator semiconductor field-effect transistor devices based on such films were used to study their transport properties. A maximum field-effect mobility of 0.038 cm−2 V−1 s−1 is reported for devices incorporating pentacene films deposited at room temperature. The structural characterization revealed the coexistence of two phases: the thermodynamically stable single-crystal phase and the kinetically favored, metastable thin-film phase. Such mixed phase films were produced when low deposition rates were used in combination with a substrate temperature of 55 °C. Mixed phase films had transport properties inferior to films consisting solely of one phase, while amorphous films deposited at low surface mobility conditions had extremely low conductivity. Use of prepurified pentacene as source material resulted in an order of magnitude lower free-carrier concentration in the pentacene film as compared to films made with as-received pentacene.

Doping is one of the most important methods to control charge carrier concentration in semiconductors. Ideally, the introduction of dopants should not perturb the ordered microstructure of the semiconducting host. In some systems, such as modulation-doped inorganic semiconductors or molecular charge transfer crystals, this can be achieved by spatially separating the dopants from the charge transport pathways. However, in conducting polymers, dopants tend to be randomly distributed within the conjugated polymer, and as a result the transport properties are strongly affected by the resulting structural and electronic disorder. Here, we show that in the highly ordered lamellar microstructure of a regioregular thiophene-based conjugated polymer, a small-molecule p-type dopant can be incorporated by solid state diffusion into the layers of solubilizing side chains without disrupting the conjugated layers. In contrast to more disordered systems, this allows us to observe coherent, free-electron-like charge transport properties, including a nearly ideal Hall effect in a wide temperature range, a positive magnetoconductance due to weak localization and the Pauli paramagnetic spin susceptibility.

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. (2017) High operational and environmental stability of high-mobility conjugated polymer fieldeffect transistors achieved through the use of molecular additives. Nature Materials, 16 (3 Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. challenge is now to achieve the required device uniformity for large-area 46 applications, such as displays. With conjugated polymers that show high field-effect 47

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