Advantage of arch-shaped structure on transistor performances over linear-shaped structure in dibenzothienopyrrole semiconductors

To understand the influence of molecular shape on the optoelectronic properties of heteroacenes, we report here the syntheses and characterizations of two linear- and two arch-shaped dibenzothienopyrrole (DBTP) derivatives, namely, N-hexyldibenzothieno[3,2-b:2′,3′-d]pyrrole (l-HDBTP), N-phenyldibenzothieno[3,2-b:2′,3′-d]pyrrole (l-PDBTP), N-hexyldibenzothieno[2,3-b:3′,2′-d]pyrrole (a-HDBTP) and N-phenyldibenzothieno[2,3-b:3′,2′-d]pyrrole (a-PDBTP). Their structure-property relationships have been systematically studied by optical absorption, cyclic voltammetry, single-crystal X-ray diffraction analyses and the single-crystal-based and thin-film-based field-effect transistors (FETs). The results demonstrate that the arch-shaped DBTP derivatives can modify their electronic structures and molecular arrangements by tuning of substituents, to obtain a better charge-transporting ability relative to the linear-shaped ones. The arch-shaped N-phenyl substituted a-PDBTP exhibits optimum molecular π-stacking arrangement and charge transport properties, with the hole mobility of 0.75 cm2V−1s−1 and 0.058 cm2V−1s−1 for the single-crystal and the thin-film OFETs, respectively. These results indicate that the arch-shaped DBTP core is a promising building block in the area of organic semiconducting materials.