We report the fabrication of devices in which one single-walled carbon nanotube spans a barrier between two fluid reservoirs, enabling direct electrical measurement of ion transport through the tube. ...A fraction of the tubes pass anomalously high ionic currents. Electrophoretic transport of small single-stranded DNA oligomers through these tubes is marked by large transient increases in ion current and was confirmed by polymerase chain reaction analysis. Each current pulse contains about 10⁷ charges, an enormous amplification of the translocated charge. Carbon nanotubes simplify the construction of nanopores, permit new types of electrical measurements, and may open avenues for control of DNA translocation.
We describe here the direct connection between the molecular conformation of a conjugated macrocycle and its macroscopic charge transport properties. We incorporate chiral, helical perylene diimide ...ribbons into the two separate macrocycles as the n-type, electron transporting material. As the macrocycles’ films and electronic structures are analogous, the important finding is that the macrocycles’ molecular structures and their associated dynamics determine device performance in organic field effect transistors. We show the more flexible macrocycle has a 4-fold increase in electron mobility in field effect transistor devices. Using a combination of spectroscopy and density functional theory calculations, we find that the origin of the difference in device performance is the ability of more flexible isomer to make intermolecular contacts relative to the more rigid counterpart.
The synthesis of an antiaromatic tetraoxa8circulene annulated with four perylene diimides (PDI), giving a dynamic non‐planar π‐conjugated system, is described. The molecule contains 32 aromatic rings ...surrounding one formally antiaromatic planarized cyclooctatetraene (COT). The intense absorption (ϵ=3.35×105 M−1 cm−1 in CH2Cl2) and emission bands are assigned to internal charge‐transfer transitions in the combined PDI‐circulene π‐system. The spectroscopic data is supported by density functional theory calculations, and nuclear independent chemical shift calculation indicate that the antiaromatic COT has increased aromaticity in the reduced state. Electrochemical studies show that the compound can reversibly reach the tetra‐ and octa‐anionic states by reduction of the four PDI units, and the deca‐anionic state by reduction of the central COT ring. The material functions effectively in bulk hetero junction solar cells as a non‐fullerene acceptor, reaching a power conversion efficiency of 6.4 %.
Annelating the antiaromatic tetraoxa8circulene with four perylenediimide units yields an intensely absorbing and emissive charge‐transfer molecule. The aromatic/antiaromatic character of neutral and charged species and the incorporation in bulk hetero junction solar cell (power conversion efficiency of 6.4 %) is described.
Two cove‐edge graphene nanoribbons hPDI2‐Pyr‐hPDI2 (1) and hPDI3‐Pyr‐hPDI3 (2) are used as efficient electron‐transporting materials (ETMs) in inverted planar perovskite solar cells (PSCs). Devices ...based on the new graphene nanoribbons exhibit maximum power‐conversion efficiencies (PCEs) of 15.6 % and 16.5 % for 1 and 2, respectively, while a maximum PCE of 14.9 % is achieved with devices based on 6,6‐phenyl‐C61‐butyric acid methyl ester (PC61BM). The interfacial effects induced by these new materials are studied using photoluminescence (PL), and we find that 1 and 2 act as efficient electron‐extraction materials. Additionally, compared with PC61BM, these new materials are more hydrophobic and have slightly higher LUMO energy levels, thus providing better device performance and higher device stability.
Blue (nano)ribbon solar cells: Two electron‐deficient graphene nanoribbons are used as the electron‐transporting materials (ETMs) in inverted perovskite solar cells (PSCs). The nanoribbons provide improved performance over the commonly used PC61BM. The most important benefits are the improved PCE (>10 % over PC61BM) and improved device lifetime owing to the hydrophobic nature of the solubilizing chains on the ribbons.
In this study, we have developed a method to create Co6Se8 superatoms in which we program the metal–ligand bonds. We exclusively form the Co6Se8 core under simple reaction conditions with a facile ...separation of products that contain differential substitution of the core. The combination of Co2(CO)8 and PR3 with excess Se gives the differentially and directionally substituted superatoms, Co6Se8(CO) x (PR3)(6–x). The CO groups on the superatom can be exchanged quantitatively with phosphines and isonitriles. Substitution of the CO allows us to manipulate the type and length of chemical bridge between two redox-active superatomic centers in order to modulate intersuperatomic coupling. Linking two superatoms together allows us to form the simplest superatom molecule: a diatomic molecule. We extend the superatom molecule concept to link three superatoms together in a linear arrangement to form acyclic triatomic molecules. These superatom molecules have a rich electrochemical profile and chart a clear path to a whole family of superatom molecules with new and unusual collective properties.
Though both the crystal structure and molecular orientation of organic semiconductors are known to impact charge transport in thin-film devices, separately accessing different polymorphs and varying ...the out-of-plane molecular orientation is challenging, typically requiring stringent control over film deposition conditions, film thickness, and substrate chemistry. Here we demonstrate independent tuning of the crystalline polymorph and molecular orientation in thin films of contorted hexabenzocoronene, c-HBC, during post-deposition processing without the need to adjust deposition conditions. Three polymorphs are observed, two of which have not been previously reported. Using our ability to independently tune the crystal structure and out-of-plane molecular orientation in thin films of c-HBC, we have decoupled and evaluated the effects that molecular packing and orientation have on device performance in thin-film transistors (TFTs). In the case of TFTs comprising c-HBC, polymorphism and molecular orientation are equally important; independently changing either one affects the field-effect mobility by an order of magnitude.
This work explores the formation of well-defined molecular p–n junctions in solution-processed self-assembled heterojunction solar cells using dodecyloxy-substituted contorted hexabenzocoronene ...(12-c-HBC) as a donor material and phenyl-C70-butyric acid methyl ester (PC70BM) as an acceptor. We find that the contorted 12-c-HBC molecules effectively assemble in solution to form a nested structure with the ball-shaped PC70BM. The result is a self-assembled molecular-scale p–n junction. When this well-defined p–n junction is embedded in active films, we can make efficient self-assembled solar cells with minimal amounts of donor material relative to the acceptor. The power conversion efficiency is drastically enhanced by the mode of donor and acceptor assembly within the film.
Stringing the Perylene Diimide Bow Liu, Taifeng; Yang, Jingjing; Geyer, Florian ...
Angewandte Chemie (International ed.),
August 17, 2020, Letnik:
59, Številka:
34
Journal Article
Recenzirano
Odprti dostop
This study explores a new mode of contortion in perylene diimides where the molecule is bent, like a bow, along its long axis. These bowed PDIs were synthesized through a facile fourfold Suzuki ...macrocyclization with aromatic linkers and a tetraborylated perylene diimide that introduces strain and results in a bowed structure. By altering the strings of the bow, the degree of bending can be controlled from flat to highly bent. Through spectroscopy and quantum chemical calculations, it is demonstrated that the energy of the lowest unoccupied orbital can be controlled by the degree of bending in the structures and that the energy of the highest occupied orbital can be controlled to a large extent by the constitution of the aromatic linkers. The important finding is that the bowing results not only in red‐shifted absorptions but also more facile reductions.
Bow to demands: A new mode of contortion in perylene diimides has been investigated, where the molecule is bent along its long axis like a bow. By adjusting the tension in the strings of the bow, the degree of bending can be controlled from flat to highly bowed. The important finding is that the bowing results not only in red‐shifted absorptions but also in more facile reductions.
Molecular building blocks are designed and created for the cis- and trans-dibrominated perylenediimides. The syntheses are simple and provide these useful materials on the gram scale. To demonstrate ...their synthetic versatility, these building blocks were used to create new dimeric perylenediimide helixes. Two of these helical dimers are twistacenes, and one is a helicene. Crucially, each possesses regiochemically defined functionality that allows the dimer helix to be elaborated into higher oligomers. It would be very difficult to prepare these helical PDI building blocks regioselectively without the methods described.
We have grown well-ordered graphene adlayers on the lattice-matched Co(0001) surface. Low-temperature scanning tunneling microscopy measurements demonstrate an on-top registry of the carbon atoms ...with respect to the Co(0001) surface. The tunneling conductance spectrum shows that the electronic structure is substantially altered from that of isolated graphene, implying a strong coupling between graphene and cobalt states. Calculations using density functional theory confirm that structures with on-top registry have the lowest energy and provide clear evidence for strong electronic coupling between the graphene π-states and Co d-states at the interface.
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