Ke Zhang, P. Wucher, T. Marszalek, M. Babics, A. Ringk, Paul W.M. Blom, P.M. Beaujuge, W. Pisula
Chem. Mater., 30 (15), pp. 5032-5040, (2018)
Long-Range Molecular Self-Assembly, p-Extended Pyrene-Functionalized Diketopyrrolopyrroles
End-group-directed molecular self-assembly can be an effective strategy in the design of “organic electronics” amenable to specific morphologies and charge transport patterns for device applications. In this study, we report on the design, self-ordering, and transistor characteristics of an analogous set of pyrene-functionalized diketopyrrolopyrroles (DPP; namely, SM1–3) obtained by “successive incorporation” of DPP motifs. The well-defined pyrene-substituted DPP analogues are systematically examined in correlation of (i) the number of incorporated DPP motifs in the π-extended main-chain and (ii) the solution-processing conditions employed for the thin film formation. Solvent vapor enhanced drop-casting (SVED) from chloroform (CHCl3) and tetrahydrofuran (THF) are found to promote very distinct, long-range morphologies of SM1–3. During THF-mediated SVED, the growth of a one-dimensional fiber of SM1–3 originates from the formation of initial aggregates in THF. In particular, extending the π-conjugation of the DPP core, and, concurrently, the number of alkyl side-chains involved, is found to mitigate the long-range self-assembly of SM1–3 and, in turn, to lower crystal size and fiber length. Field-effect transistors based on SM3 exhibit ambipolar behavior, demonstrating the relevance of pyrene-functionalized diketopyrrolopyrroles in the design and development of solution-processed ambipolar small-molecule semiconductors.