High Anisotropy of the Field-Effect Transistor Mobility in Magnetically Aligned Discotic Liquid-Crystalline Semiconductors

Abstract

A magnetic field has been utilized for producing highly oriented films of a substituted hexabenzocoronene (HBC). Optical microscopy studies revealed large area HBC monodomains that covered the entire film, while wide-angle X-ray measurements showed that the HBC molecules are aligned with their planes along the applied field. On the basis of this method, solution-processed field-effect transistors (FET) have been constructed with charge carrier mobilities of up to 10(-3) cm2/V.s, which are significantly enhanced with respect to the unaligned material. Exceptionally high mobility anisotropies of 25-75 for current flow parallel and perpendicular to the alignment direction have been measured as a function of the channel length. Atomic force microscopy performed on the FET structures reveals fibril superstructures that are oriented perpendicularly to the magnetic field direction, consisting of molecular columns with a slippage angle of 40 degrees between the molecules. For channel lengths larger than 2.5 mum, the fibrils are smaller than the electrode spacing, which adversely affects the device performance.

Relaxation dynamics in the columnar liquid crystal phase of hard platelets

“…16,20 Remarkably, the spontaneous supramolecular self-assembly in ordered columnar aggregates increases the mobility of electrons and charge carriers through the cores and along the stacked arrangements. 21,22 Due to the insulating effect of the lateral hydrocarbon chains, the interactions established between neighboring mesogens within the same column are significantly stronger than those between mesogens of contiguous columns, 23,24 and a (quasi) 1D charge transport is observed. [25][26][27] As a consequence of this peculiar behavior, the conducting properties of CLCDs offer the advantage to improve the performance of electronic, optoelectronic, and photovoltaic devices, such as solar cells and plastic organic field-effect transistors.…”

Controlled Growth of Large‐Area High‐Performance Small‐Molecule Organic Single‐Crystalline Transistors by Slot‐Die Coating Using A Mixed Solvent System

“…Therefore, many deposition techniques have been used for patterning and alignment of organic semiconductors. Among them, frictiontransfer, [ 12 ] rubbing alignment, [ 13 ] photoalignment, [ 14 ] magnetic alignment, [ 15 ] Langmuir-Blodgett (LB), [ 16 ] zone-casting, [ 17 ] and solution-shearing techniques, [ 18 ] etc., are promising to produce highly aligned thin fi lms. However, most of these techniques are not suitable for convenient, large-area commercial production.…”

A Highly Ordered Material from Magnetically Aligned Peptide Amphiphile Nanofiber Assemblies

“…Therefore, for single molecules, this energy, determined by Dv m , is very small compared to its inherent thermal energy and only a collective behavior of molecules will allow for alignment to occur. Normal Brownian motion can already disrupt any alignment of single molecules, and this technique therefore only works well when molecules are very large, [12][13][14] contain moieties with high magnetic susceptibility, such as aromatic units, [15] and are preassembled, as in the case of, for example, liquid crystalline materials, [16,17] where the forces are cooperatively additive. To date, this has led to a moderate number of type of biomaterials that have been aligned magnetically, such as proteins such as fibrin, [18] collagen [19,20] and tubulin, [21] helix-turn-helix peptides, [22] viruses [23] and phages, [24,25] nucleic acids, [26] and phospholipids.…”