Thin-film morphology and transistor performance of alkyl-substituted triethylsilylethynyl anthradithiophenes

Studies of soluble small-molecule semiconductors based on pentacene and anthradithiophene chromophores have generally shown that molecules with strong two-dimensional solid-state interactions yield high-performance thin-film transistors, while similar compounds with one-dimensional solid-state interactions form thin-film devices with significantly worse performance. As a further exploration of this issue, we describe here the synthesis and device characterization of soluble anthradithiophene derivatives functionalized at the periphery of the chromophore with small (C₁-C₃) alkyl chains that subtly alter the solid-state arrangements of the molecules. We demonstrate that these changes in crystal packing have significant impact on both thin-film formation and field-effect mobility. In general, materials with even nominal two-dimensional close contacts between molecules tended also to exhibit two-dimensional film growth, and generally better device performance than those with strictly one-dimensional interactions.