Field‐Force Alignment of Disc‐Type π Systems

Abstract

The ability of electric fields to align nonpolar semiconducting molecules was demonstrated using hexa(para-n-dodecylphenyl)hexabenzocoronene (HBC-PhC12) as a model compound. A solution of HBC-PhC12 was applied to a glass surface by drop-casting and the molecules were oriented into highly ordered structures by an electric field during solvent evaporation. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) showed a long-range alignment where the disclike molecules were organized in columns perpendicular to the direction of the imposed electric field. The high anisotropy of the uniaxially aligned films was characterized by cross-polarized light microscopy. The birefringence of the HBC-PhC12 films was related to the presence of extended domains of unidirectionally aligned columns in which the aromatic cores of the HBC-PhC12 molecules were perpendicular to the columnar axis. The packing and the arrangement of the molecules in the field-force ordered films were proven by electron diffraction and X-ray analyses.

Electric Field Tuning Molecular Packing and Electrical Properties of Solution‐Shearing Coated Organic Semiconducting Thin Films

“…In addition to the above parameters, the use of electrical field for alignment and placement of organic electronic materials has also been reported in examples such as alignment of liquid crystals and OSC crystallites, manipulation of OSC solution droplets, self‐assembly of organic fibers, and morphology modification of polymer blends . These works were mostly descriptive and proposed heuristic explanations to the interaction between field and matter.…”

Hierarchical Self‐Assembly of Edge‐On Nanocolumnar Superstructures of Large Disc‐Like Molecules

“…For example, porphyrins, [3] phthalocyanines, [4] triphenylenes, [5] and hexa-peri-hexabenzocoronenes (HBCs) [6] can form uniaxial alignments lying horizontal on different types of substrates by using appropriate techniques. These techniques include zone casting, [6c] frictiontransferred PTFE templates, [1c,7] Langmuir-Blodgett films, [8] stationary nozzles onto a moving substrate, [9] and more recently magnetic field-induced, [10] field-force alignment, [11] and circularly polarized infrared irradiation. [12] However, the lateral resolution of the uniaxial alignments in these studies is limited to a few nanometers and the growth of the columns is induced either by a field (magnetic or electrical), a mechanical constraint, or a dewetting process.…”

Self-assembled 1D Semiconductors: Liquid Crystalline Columnar Phase

“…Thus, alignment by electric field was achieved in the columnar phases of corannulene, triphenylene, hexaphenylbenzene, hexabenzocoronene and phthalocyanine based DLCs. In one of the first demonstrations, a solution of hexa(para-n-dodecylphenyl)hexabenzocoronene (8b) was applied to a glass surface by drop-casting and the molecules were oriented into highly ordered planar aligned columnar structures by an electric field during solvent evaporation [134]. An amide-substituted corannulene derivative with branched paraffinic side chains was shown to self-assemble into a columnar phase that responds to an applied electric field and align homeotropically to the electrode surface [135].…”