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MRI SEMINAR Dr Laure Biniek, CNRS, Strasbourg - Highly oriented and crystalline semi-conducting and conducting polymer films prepared by high-temperature rubbing

Date: 1 November 2017   Time: 15:00 - 16:00

This presentation focuses on recent advances in growth control and oriented crystallization of semi-conducting and conducting polymers for plastic electronic applications. The performance and lifetime of organic electronic devices are critically dependent on the properties of both active materials and interfaces. For instance both molecular and crystalline orientations of polymeric semi-conducting materials determine optical, electronic and opto-electronic properties in thin films since these properties are by essence highly anisotropic. Therefore, it is of interest to control the contact plane of crystalline domains in the active layers as it determines, for instance, the direction of facile charge transport in the cases of organic solar cells and organic field effect transistors. Particular emphasis will be given to the progress made in high-temperature rubbing of such polymers. This effective large scale alignment method can orient a large palette of polymer semiconductors (PSCs) with n- or p-type character without the use of an alignment substrate.1 The concurrent roles of the polymer molecular weight distribution and the rubbing temperature (TR) on the in-plane orientation have been rationalized for P3HT and PBTTT.2a Correlations are drawn between nanomorphology/crystallinity on one side and charge transport and optical properties on the other side. It is shown that the exciton bandwidth in P3HT crystals is determined by the length of the average planarized chain segments in the crystals. The high alignment and crystallinity observed for TR > 200 °C cannot translate to high hole mobilities parallel to the rubbing because of the adverse effect of amorphous interlamellar zones interrupting charge transport between crystalline lamellae.2b In a second part of this presentation, we show that soft doping of aligned PSCs yields highly oriented conducting polymer films with anisotropic charge conductivity and thermoelectric properties that are enhanced along the rubbing direction. The unique in-plane orientation in such conducting polymer films helps rationalizing the mechanism of redox doping.2c

References.
1. M. Brinkmann, L. Hartmann, L. Biniek, K. Tremel and N. Kayunkid Macromolecular Rapid. Comm. 2014, 35, 9.
2. a) L. Biniek, S. Pouget, D. Djurado, E. Gonthier, K. Tremel, N. Kayunkid, E. Zaborova, N. Crespo-Monteiro, O. Boyron, N. Leclerc, S. Ludwigs, and M. Brinkmann, Macromolecules 2014, 47, 3871. b) A. Hamidi-Sakr, L. Biniek, S. Fall, M. Brinkmann Adv. Funct. Mater. 2016, 26, 408. C) A. Hamidi-Sakr, L. Biniek, J.-L. Bantignies, D. Maurin, L. Herrmann, N. Leclerc, P. Lévêque, V. Vijayakumar, N. Zimmermann, and M. Brinkmann Adv. Funct. Mater. 2017, 1700173.

Location:  David Sizer Theatre