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Azeotropic binary solvent mixtures for preparation of organic single crystals

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Author: Li, X. · Kjellander, B.K.C. · Anthony, J.E. · Bastiaansen, C.W.M. · Broer, D.J. · Gelinck, G.H.
Type:article
Date:2009
Institution: TNO Industrie en Techniek
Source:Advanced Functional Materials, 22, 19, 3610-3617
Identifier: 279967
doi: doi:10.1002/adfm.200901353
Keywords: Abrupt transition · Active Layer · Azeotropic points · Binary solvent mixtures · Binary solvents · Conjugated organic molecules · Homogeneous solutions · In-field · New approaches · Organic molecules · Organic single crystals · Pentacenes · Polycrystalline · Self-assembled · Solvent composition · Binary mixtures · Carrier mobility · Field effect transistors · Morphology · Solvents · Trichloroethylene · Single crystals

Abstract

Here, a new approach is introduced to prepare large single crystals of π-conjugated organic molecules from solution. Utilizing the concept of azeotropism, single crystals of tri-isopropylsilylethynyl pentacene (TIPS-PEN) with dimensions up to millimeters are facilely self-assembled from homogeneous solutions comprising two solvents with opposing polarities and a positive azeotropic point At solvent compositions close to the azeotropic point, an abrupt transition of morphology from polycrystalline thin-films to large single crystals is found. How to adjust the initial ratio of the binary solvents so that the change in solvent composition during evaporation favors the specific H-aggregation and promotes an efficient self-assembly of TIPS-PEN is explained. The charge-carrier (hole) mobilities are substantially enhanced by a factor of 4 from the morphology of thin-films to large single crystals used as active layer in field-effect transistors. Additionally this approach is extended to other π-π stacked organic molecules to elucidate its broad applicability. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.