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Azeotropic Binary Solvent Mixtures for Preparation of Organic Single Crystals

Xiaoran Li, B. K. Charlotte Kjellander, John E. Anthony, Cornelis W. M. Bastiaansen, Dirk J. Broer, and Gerwin H. Gelinck, Weinheim (2009)

Here, a new approach is introduced to prepare large single crystals of pi-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 pi–pi stacked organic molecules to elucidate its broad applicability.

Partners : TNO

Place of Publication : Weinheim

Date of Publication : 2009/10/02

Additional Data : Adv. Funct. Mater. 2009, 19, 3610–3617

Link to the online version of the article.