Theoretical study on charge transport properties of cyanovinyl-substituted oligothiophenes

When the oligothiophene is substituted by dicyanovinyl (DCV) or tricyanovinyl (TCV) group, how does its transport property change? Here, we will mainly focus on exploring the influence on charge transport properties of introducing a strong electron-withdrawing DCV/TCV group to the thiophene units within Marcus–Levich–Jortner formalism at the level of density functional theory. The results show that the introduction of cyanovinyl-substituents improves the molecular π-stacking, decreases the frontier molecular orbital energy levels and reorganization energies, and increases the transfer integrals and mobilities, comparing with their parent thiophene molecules. It is interesting to find the phenomenon that enriching intermolecular interactions can be favorable for controlling the transport channel and thus get high mobility, which would be shown by the angular resolution anisotropic mobilities analysis. Besides, the simulated packing motifs of dimers for 3a and 3b without crystal structures reported indicate that their packing may form the slip π–π stacking, and that 3b may be a good ambipolar material. In a word, compared with corresponding thiophene analogues and tetracyanoquinodimethane, these compounds may become the candidates for the n-type or ambipolar organic semiconductor materials.

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► Cyanovinyl can improve and tune the type and size of mobility of oligothiophene.
► Enriching intermolecular interaction is conducive to obtain higher mobility.
► Distinct and anisotropic mobility is due to different intermolecular interaction.