Supramolecular Approaches to Nanoscale Morphological Control in Organic Solar Cells

Having recently surpassed 10% efficiency, solar cells based on organic molecules are poised to become a viable low-cost clean energy source with the added advantages of mechanical flexibility and light weight. The best-performing organic solar cells rely on a nanostructured active layer morphology consisting of a complex organization of electron donating and electron accepting molecules. Although much progress has been made in designing new donor and acceptor molecules, rational control over active layer morphology remains a central challenge. Long-term device stability is another important consideration that needs to be addressed. This review highlights supramolecular strategies for generating highly stable nanostructured organic photovoltaic active materials by design

Understanding and controlling the growth of metals and molecules on an insulating surface

Noncontact atomic force microscopy (NC-AFM) was applied to investigating the creation of monatomic depth rectangular pits, the growth of metals, and the templated growth of molecules on the KBr (001) surface under ultrahigh vacuum conditions. The pits were produced by a new method where the sample is exposed to a controlled dose of charge from an electron beam evaporator. The structure and size distribution of the pits was characterized by NC-AFM. For the metal growth studies, gold, tantalum, and palladium were deposited onto KBr by electron beam deposition. The gold produced tall multiply twinned and epitaxial nanoparticles, while the tantalum formed flatter fractal islands. The palladium growth resulted in the creation of rectangular KBr islands in addition to palladium nanoparticles. Despite the use of a charge deviating grid, charge played an important role during the metal growth. In particular, the number density of gold nanoparticles followed nearly the same temperature dependence as the pits, suggesting that the metal nanoparticles nucleate predominantly at defect sites created by incident charge. The effect of charge was also seen in the tantalum system where pits surrounded the nanoparticles prepared at elevated temperatures. By creating pits before depositing gold, it was shown that the pits edges can be used to template the growth of metals. It was also shown that the pits can be used to trap PTCDA molecules and to align C60 molecules with the <100> direction of the substrate. Molecular resolution NC-AFM measurements were used to determine the structures and lattice constants of the molecular nanostructures. Experiments involving the sequential growth of metals and molecules showed that the order of deposition and the strength of the molecule-metal interaction are key factors in determining the nature of the growth. Furthermore, it was shown that metal structures can be used to nucleate the growth of sufficiently strongly interacting molecules

Use of an Electron-Beam Evaporator for the Creation of Nanostructured Pits in an Insulating Surface

We demonstrate a method for creating monatomic-depth rectangular pits of controlled size in an alkali halide surface by using an electron-beam evaporator. Atomic resolution noncontact atomic force microscopy is used to characterize the structure and size distribution of the pits, with mean side lengths ranging from 6.5 to 20 nm. It is also demonstrated that metal nanoparticles can be used to nucleate the growth of pits, resulting in pits with metal nanoparticles inside

Face-on stacking and enhanced out-of-plane hole mobility in graphene-templated copper phthalocyanine

Efficient out-of-plane charge transport is required in vertical device architectures, such as organic solar cells and organic light emitting diodes. Here, we show that graphene, transferred onto different technologically-relevant substrates, can be used to induce face-on molecular stacking and improve out-of-plane hole transport in copper phthalocyanine thin films

Intergration of self-assembled discotic-based fibres into fild-effect transistors :a comparaison of preparation approaches

info:eu-repo/semantics/publishe

Integration of self-assembled discotic-based fibres into field-effect transistors: a comparison of preparation approaches

The role played by the preparation method upon the morphological and electrical properties of alkyl substituted thio-triphenylene-based self-assembled fibres is explored by comparing two processing approaches, termed solvent vapour annealing (SVA) and solvent induced precipitation (SIP). Both approaches led to fibres having widths of several hundred nanometres and lengths of tens of micrometres. SVA formed isolated fibres which were tens of nanometres high, flat, and tapered at the ends. Conversely, SIP fibres exhibited nearly matching heights and widths, but organized into bundles. Despite these morphological differences, the same intermolecular packing is found by XRD in each type of structure, albeit with differing degrees of long-range order. The fibres were integrated into bottom-gate bottom-contact field-effect transistors. The density and configuration of the fibres with respect to the electrodes and gate dielectric were found to play an important role in the transport properties. SIP devices yielded the highest mobilities compared to SVA and spin-coated devices, largely owing to their high degree of internal order and the possibility to achieve high fibre densities within the transistor channel. © The Royal Society of Chemistry.SCOPUS: ar.jinfo:eu-repo/semantics/publishe