Towards high charge-carrier mobilities by rational design of the shape and periphery of discotics

Abstract

Discotic liquid crystals are a promising class of materials for molecular electronics thanks to their self-organization and charge transporting properties. The best discotics so far are built around the coronene unit and possess six-fold symmetry. In the discotic phase six-fold-symmetric molecules stack with an average twist of 30 degrees, whereas the angle that would lead to the greatest electronic coupling is 60 degrees. Here, a molecule with three-fold symmetry and alternating hydrophilic/hydrophobic side chains is synthesized and X-ray scattering is used to prove the formation of the desired helical microstructure. Time-resolved microwave-conductivity measurements show that the material has indeed a very high mobility, 0.2 cm(2) V(-1) s(-1). The assemblies of molecules are simulated using molecular dynamics, confirming the model deduced from X-ray scattering. The simulated structures, together with quantum-chemical techniques, prove that mobility is still limited by structural defects and that a defect-free assembly could lead to mobilities in excess of 10 cm(2) V(-1) s(-1).

Evolution of Graphene Molecules: Structural and Functional Complexity as Driving Forces behind Nanoscience

“…There is, admittedly, an appreciable gap between nanometer-sized, molecularly defined graphenes 42 and the micron-sized graphene flakes made by top-down methods. Before we start to close this gap synthetically, let us take a brief look at the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 high charge carrier mobility for graphene, 43,44 which would qualify graphene as a useful semiconductor in a high-modulation FET.…”

First principles view on chemical compound space: Gaining rigorous atomistic control of molecular properties

“…[113] PAHs form discotic liquid crystals which self-assemble into columnar liquid crystal structures, implying their usefulness for organic photovoltaic applications. 122 In this section, we will discuss the application of ab initio statistical learning approaches to previously obtained first principles data for N compounds. Merely based on the data, QSPRs can be ' 'learned,' ' and subsequently be used to avoid the cumbersome task of having to explicitly model all the underlying physical degrees of freedom of electrons and nuclei.…”

π-Conjugated polymer-layered structures: synthesis and self-assembly

“…[3][4][5][6][7][8][9][10][11] Because π-conjugated compounds tend to aggregate by π-π stacking, the introduction of non-covalent interactions at appropriate positions increases their association constants and facilitates the formation of higher-ordered structures. 12,13 For example, supramolecular gels can be formed through intermolecular interactions such as hydrogen bonds, 14,15 and multiple long alkyl chains facilitate columnar stacking along the π-stacking direction of supramolecular assemblies [16][17][18][19] (Figure 1a).…”