Uniaxial Alignment of the Columnar Super-Structure of a Hexa (Alkyl) Hexa-<i>peri</i>-hexabenzocoronene on Untreated Glass by Simple Solution Processing

Tracz, A.; Jeszka, J.K.; Watson, Mark D.; Pisula, Wojciech; Müllen, Kläus; Pakuła, Tadeusz

doi:10.1021/ja028945z

Cited by 248 publications

(213 citation statements)

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“…A. Woollam Co., based on the rotating analyzer principle. 20 A temperature-controlled heat cell purged with inert He gas was used for all measurements. The sample was oriented with the cast direction of the film at 45°with respect to the plane of incidence inside the heat cell.…”

Section: Methodsmentioning

confidence: 99%

“…The resulting films are thin, transparent, homogeneous, and with a highly reproducible biaxially oriented crystalline structure. 20,16 Grazing Incidence X-ray Diffraction (GID). The GID studies were performed using the z-axis diffractometer at the wiggler beamline BW2 at Hasylab.…”

Section: Methodsmentioning

confidence: 99%

“…The HBC-C 12 H 25 was synthesized as described elsewhere. 19 For obtaining the films, zone casting was employed, 20 giving a high degree of in-plane alignment without using aligning substrates, stretching, or rubbing. The resulting films are thin, transparent, homogeneous, and with a highly reproducible biaxially oriented crystalline structure.…”

Section: Methodsmentioning

confidence: 99%

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In Situ Studies of Phase Transitions in Thin Discotic Films

et al. 2005

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The crystalline to liquid crystalline (Cr-LC) phase transition in thin films of zone-cast hexa-perihexabenzocoronene sixfold substituted with dodecyl side chains (HBC-C 12 H 25 ) has been studied in detail using grazing incidence X-ray diffraction (GID), electron diffraction (ED), and variable angle spectroscopic ellipsometry (VASE), When heating the material, a first minor transition is observed around 42°C. This change is attributed to alterations of the crystalline alkyl chain packing, which only slightly changes the electronic properties of the material. At higher temperatures of about 90°C, but still significantly below the previously reported transition temperature in bulk, the Cr-LC transition is observed. An accompanying large increase in optical anisotropy is compatible with the X-ray data, showing a transition from the as-cast herringbone-like crystalline state to a highly ordered discotic hexagonal columnar LC phase. The structural transition has the macroscopic effect of increasing the film thickness. The high structural order of the as-cast low-temperature phase is only partly recovered after cooling, and the phase transition exhibits a large hysteresis. From the ellipsometry data, the dielectric tensor of HBC-C 12 H 25 was refined to unprecedented detail. IntroductionOrganic electronics have promising prospects, with the main motivation being to make cheap plastic sensors and circuits. 1 The importance of well-defined molecular order to exploit the highly anisotropic properties of the specifically designed molecules is well-recognized. A requirement for good mobility in films of organic conjugated molecules is a good overlap of the π-electrons of neighboring molecules. Many pathways are being explored to achieve self-assembled highly connected networks of π-π interacting molecules, including both chemical modifications 2-4 and processing techniques. [5][6][7][8][9][10][11][12] Discotics, i.e., planar, disc-shaped aromatic molecules, have been intensely studied during the past two decades. To make them soluble and to control the thermal properties, they are substituted with side chains at the periphery. The molecules tend to segregate into stacked columns of the aromatic cores, separated by less-ordered side chains. These stacks can be considered one-dimensional molecular wires, whereas the side chains, typically alkyl, are electronically inactive. A relatively high mobility of typically 1.0 cm 2 /V s is obtained in these materials. 13 The molecules studied here, hexa-peri-hexabenzocoronenes (HBC; see Figure 1) are graphenes, having delocalized electrons on both sides of the molecular plane. Underivated HBC is highly crystalline and poorly soluble. Because of electrostatic quadrupolar interactions, the molecules tend to pack in the so-called herringbone structure.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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In Situ Studies of Phase Transitions in Thin Discotic Films

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“…Hexa-peri-hexabenzocoronenes (HBSs) 10 exhibit one of the highest intrinsic charge carrier mobilities for a discotic material (Van de Craats & Warman 2001). Their syntheses are based on the planarization of suitable hexaphenylbenzenes 9 by oxidative cyclodehydrogenation, which is formed either by cyclotrimerization of diphenylacetylenes 7 (i) or by Diels-Alder cycloaddition (ii) of a tetraphenylcyclopentadienone 8 to a diphenylacetylene 7 (Berresheim et al 1999; scheme 3).…”

Section: Graphite Moleculesmentioning

confidence: 99%

“…In a device, the semiconducting columns must be aligned perpendicular to the electrodes, which requires an edge-on orientation for FETs or a face-on orientation for a photovoltaic device ; figure 5). Two methods have been used to produce aligned films of HBCs on a surface: (i) spin casting of a solution of HBCs on a preoriented polytetrafluoroethylene (PTFE) layer using the surface roughness or (ii) zone casting from the solution or melt (Tracz et al 2003;Pisula et al 2005a; figure 6). …”

Section: Supramolecular Arrays: Formation Processing and Optimizatiomentioning

confidence: 99%

Expanding benzene to giant graphenes: towards molecular devices

Müller

Müllen

2007

Phil. Trans. R. Soc. A.

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Phenylene-based conjugated materials provide versatile platforms for the development of molecular devices. Architectures of one-and two-dimensional polyphenylenes, which self-assemble into three-dimensional objects with advantageous electronic properties, have been investigated. Systematic relations between the size, substitution and shape with function were found, which enabled the further optimization of the materials. Hand in hand with the development of suitable methods for visualization and processing, promising results were obtained for performance of nanoscale electronic devices.

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Polymer Solar Cells

Güneş

Egbe

Sariçiftçi

2011

Encyclopedia of Polymer Science and Technology

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Polymer solar cells are developing rapidly. The cost effective manufacturing, flexibility and the integration possibilities make them attractive alternatives to conventional Si‐based solar cells. Power conversion efficiencies more than 8% were reported recently by industrial companies. However, even this value has to be improved to be competitive with the other solar cell devices. There is a great amount of interdisiplinary science to be explored within the organic solar cell research, ranging from solid state device physics, photophysics, polymer synthesis, polymer processing and supramolecular chemistry. In this encyclopedia entry, we give an overview of the basic operational principles, limitations and the possible improvements for polymer solar cells.

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Uniaxial Alignment of the Columnar Super-Structure of a Hexa (Alkyl) Hexa-peri-hexabenzocoronene on Untreated Glass by Simple Solution Processing

Cited by 248 publications

References 19 publications

In Situ Studies of Phase Transitions in Thin Discotic Films

In Situ Studies of Phase Transitions in Thin Discotic Films

Expanding benzene to giant graphenes: towards molecular devices

Polymer Solar Cells

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