Self-assembly of thienylenevinylene molecular wires to semiconducting gels with doped metallic conductivity

Oligo(thienylenevinylene) (OTV) based gelators with high conductivity are reported. When compared to OTV1, OTV2 having an increased conjugation length forms relatively strong gels with a metallic conductivity of 4.8 S/cm upon doping which is the highest value reported for an organogelator. This new class of conducting gels is expected to be useful for organic electronics and photonics application, particularly for bulk heterojunction devices

Oligo(p-phenylene-ethynylene)-derived super-π-gelators with tunable emission and self-assembled polymorphic structures

Linear π-conjugated oligomers are known to form organogels through noncovalent interactions. Herein, we report the effect of π-repeat units on the gelation and morphological properties of three different oligo(p-phenylene-ethynylene)s: OPE3, OPE5, and OPE7. All of these molecules form fluorescent gels in nonpolar solvents at low critical gel concentrations, thereby resulting in a blue gel for OPE3, a green gel for OPE5, and a greenish yellow gel for OPE7. The molecule–molecule and molecule–substrate interactions in these OPEs are strongly influenced by the conjugation length of the molecules. Silicon wafer suppresses substrate–molecule interactions whereas a mica surface facilitates such interactions. At lower concentrations, OPE3 formed vesicular assemblies and OPE5 gave entangled fibers, whereas OPE7 resulted in spiral assemblies on a mica surface. At higher concentrations, OPE3 and OPE5 resulted in super-bundles of fibers and flowerlike short-fiber agglomerates when different conditions were applied. The number of polymorphic structures increases on increasing the conjugation length, as seen in the case of OPE7 with n=5, which resulted in a variety of exotic structures, the formation of which could be controlled by varying the substrate, concentration, and humidity

Light-induced ostwald ripening of organic nanodots to rods

Ostwald ripening allows the synthesis of 1D nanorods of metal and semiconductor nanoparticles. However, this phenomenon is unsuccessful with organic π-systems due to their spontaneous self-assembly to elongated fibers or tapes. Here we demonstrate the uses of light as a versatile tool to control the ripening of amorphous organic nanodots (ca. 15 nm) of an azobenzene-derived molecular assembly to micrometer-sized supramolecular rods. A surface-confined dipole variation associated with a low-yield (13–14%) trans–cis isomerization of the azobenzene moiety and the consequent dipole–dipole interaction in a nonpolar solvent is believed to be the driving force for the ripening of the nanodots to rods

Self-Assembly of Thienylenevinylene Molecular Wires to Semiconducting Gels with Doped Metallic Conductivity

Oligo(thienylenevinylene) (OTV) based gelators with high conductivity are reported. When compared to OTV1, OTV2 having an increased conjugation length forms relatively strong gels with a metallic conductivity of 4.8 S/cm upon doping which is the highest value reported for an organogelator. This new class of conducting gels is expected to be useful for organic electronics and photonics application, particularly for bulk heterojunction devices

Insight into the energy loss in organic solar cells based on benzotrithiophene copolymers: A dark current analysis at low temperature

Abstract Owing to the formation of the charge transfer (CT) state, the open-circuit voltage (V oc) of organic photovoltaic (OPV) devices commonly suffers an energy loss of 0.8–1.3 eV from the effective bandgap. Benzotrithiophene (BTT)-based low-bandgap polymers that we have recently reported showed deep HOMO levels (−5.4 to −5.6 eV) and moderate optical bandgaps of 1.7–1.8 eV, which resulted in high V oc’s of 0.78–0.98 V and relatively low energy losses when blended with methano[60]fullerene (PCBM). Here, we report the temperature-dependent dark current analysis of organic solar cells of BTT copolymers:PCBM blends. Shockley diode analyses revealed the dominant contribution of CT energy and concomitant pre-exponential factor of dark saturation current density associated with charge recombination. The findings could establish a fundamental aspect to draw a design rule in BTT-based polymers towards their evolutions in OPV devices.</jats:p

p/n-Polarity of thiophene oligomers in photovoltaic cells: role of molecular vs. supramolecular properties

The effect of molecular and supramolecular properties on the p/n-polarity of two thiophene oligomers in bulk heterojunction solar cells is described.</p

Light-Induced Ostwald Ripening of Organic Nanodots to Rods

Ostwald ripening allows the synthesis of 1D nanorods of metal and semiconductor nanoparticles. However, this phenomenon is unsuccessful with organic π-systems due to their spontaneous self-assembly to elongated fibers or tapes. Here we demonstrate the uses of light as a versatile tool to control the ripening of amorphous organic nanodots (ca. 15 nm) of an azobenzene-derived molecular assembly to micrometer-sized supramolecular rods. A surface-confined dipole variation associated with a low-yield (13–14%) <i>trans–cis</i> isomerization of the azobenzene moiety and the consequent dipole–dipole interaction in a nonpolar solvent is believed to be the driving force for the ripening of the nanodots to rods