Electronic structure and microscopic charge-transport properties of a new-type diketopyrrolopyrrole-based material.

Recently, diketopyrrolopyrrole (DPP)-based materials have attracted much interest due to their promising performance as a subunit in organic field effect transistors. Using density functional theory and charge-transport models, we investigated the electronic structure and microscopic charge transport properties of the cyanated bithiophene-functionalized DPP molecule (compound 1). First, we analyzed in detail the partition of the total relaxation (polaron) energy into the contributions from each vibrational mode and the influence of bond-parameter variations on the local electron-vibration coupling of compound 1, which well explains the effects of different functional groups on internal reorganization energy (λ). Then, we investigated the structural and electronic properties of compound 1 in its isolated molecular state and in the solid state form, and further simulated the angular resolution anisotropic mobility for both electron- and hole-transport using two different simulation methods: (i) the mobility orientation function proposed in our previous studies (method 1); and (ii) the master equation approach (method 2). The calculated electron-transfer mobility (0.00003-0.784 cm(2) V(-1) s(-1) from method 1 and 0.02-2.26 cm(2) V(-1) s(-1) from method 2) matched reasonably with the experimentally reported value (0.07-0.55 cm(2) V(-1) s(-1) ). To the best of our knowledge, this is the first time that the transport parameters of compound 1 were calculated in the context of band model and hopping models, and both calculation results suggest that the intrinsic hole mobility is higher than the corresponding intrinsic electron mobility. Our calculation results here will be instructive to further explore the potential of other higher DPP-containing quinoidal small molecules.