Frédéric Lincker

Fluorenone core donor–acceptor–donor π-conjugated molecules end-capped with dendritic oligo(thiophene)s: synthesis, liquid crystalline behaviour, and photovoltaic applications

We have synthesized a new series of donor–acceptor–donor (D–A–D) π-conjugated molecules, consisting of fluorenone core end-capped with dendritic oligo(thiophene)s of increasing generation (abbreviated as FG0, FG1, and FG2). In view of the application of these new organic semiconductors in photovoltaic devices, we have explored their spectroscopic, redox, and structural properties. The thermal behaviour of the new organic semiconductors was investigated by differential scanning calorimetry and polarized-light optical microscopy. Liquid crystalline behaviour has been found in the case of FG1, corresponding to a smectic ordering with a triclinic symmetry (Smobl) upon heating, as confirmed by variable temperature small-angle X-ray diffraction studies. In order to evaluate their photovoltaic performances, devices with an active area of 0.28 cm2 were fabricated. Under AM1.5 simulated sunlight (100 mW cm−2) conditions, a device containing FG1/[70]PCBM blends showed a power conversion efficiency of ca. 0.8%.

Rolic ® LCMO Photo Alignment Technology: Mechanism and Application to Large LCD Panels

Rolic® Light Controlled Molecular Orientation (LCMO) technology is the basis for todays advanced mass production technologies for large LCD-TV panel, high-resolution 3D patterned-retarders and high-resolution optical security devices. This fundamental technology allows an easy achievement of high resolution azimuthal LC-director patterns with defined bias angles, from homogeneous planar to homeotropic orientation, depending on the target application [1-7]. In addition to the control of bias angles, LCD panel manufacturers require alignment layers with a wide range of optimized properties. Thin alignment films must be easily coatable and should have high photosensitivity in order to achieve fast processing. The photoalignment film should also have high stability and good electrical properties such as Voltage Holding Ratio (VHR), Residual DC (RDC) and image sticking. Because of in-situ photo crosslinking during processing [1, 2], our proprietary LCMO photoalignment technology is shown to be thermally and optically stable. Last years, enormous progress has been made in the development of advanced materials that meet all requirements for mass production of large-area flat panel displays. LCMO-VA technology, for vertical alignment LCDs, is the basis for the state of the art UV2 A production technology recently used in the manufacturing of advanced new generation LCD-TV panel displays with reduced production costs and low energy consumption [8, 9]. LCMO-VA mechanism and performances of state of the art materials will be discussed.

Pi-Conjugated Molecular Nanowire Stacks Investigated by Frequency-Modulation Atomic Force Microscopy in the qPlus Configuration

Self-assembled pi-conjugated nanowire stacks were imaged using a tuning-fork probe mounted in the qPlus configuration in frequency modulation mode under ultrahigh vacuum. High resolution topographic and dissipation images demonstrate the applicability of such probes to soft conjugated materials, with sub-molecular resolution achieved perpendicular to the stacking axis. A new insight is gained from the damping contrast into the local mechanical properties of edge-on pi-conjugated stacks.

Local contact potential difference of molecular self-assemblies investigated by Kelvin probe force microscopy

Self-assembled pi-conjugated oligomer nanowires have been investigated by frequency modulation atomic force microscopy and amplitude modulation Kelvin probe force microscopy under ultra high vacuum. The distance dependence of the contact potential difference (CPD) has been analyzed by combining high resolution imaging with distance-spectroscopy measurements. It is shown that the apparition of a damping contrast characterizes the onset of short range electrostatic (SRE) forces, which are responsible for the occurrence of local CPD (LCPD) modulations correlated with the molecular lattice. By working at the onset of the damping contrast, the tip-surface separation can be adjusted to minimize the contribution of SRE forces to the measured CPD.

E2F factors rate controls the dual role of CDE/E2F composite element: A model of E2F-regulated gene expression in plant development

The promoters of several E2F‐regulated genes identified in plants contain a variety of E2F motifs, notably a composite element consisting of a “CDE‐like element” C/GGCGG on one strand, described as repressor in animals, associated with an E2F element on the complementary strand. This detailed study throughout plant development using ribonucleotide reductase promoters, allows us to propose a model, where E2F and composite elements play a dual role. Such regulation is mainly conditioned by the availability of E2F factors in tissues and during the cell cycle in tobacco.