Thin-film morphology and transistor performance of alkyl-substituted

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 onedimensional 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.