A novel electron-deficient building unit, dithienylthienothiophenebisimide, and its polymers (PTBIs) are reported. Organic photovoltaic (OPV) cells based on PTBIs as p-type material exhibit 8.0% efficiencies with open-circuit voltages higher than 1 V. Interestingly, PTBIs also function as n-type material in OPVs depending on the molecular structure. These polymers also exhibit p-channel, n-channel, and ambipolar behaviors in field-effect transistors.
We report on the results of experimental and theoretical studies on the electronic structure of gas-phase diindenoperylene (DIP) and DIP-monolayer (ML) on Cu(111). Vapor-phase ultraviolet photoelectron spectroscopy (UPS) was realized for 11.3 mg of DIP, giving reference orbital energies of isolated DIP, and UPS and inverse photoemission spectroscopy of DIP-ML/graphite were performed to obtain DIP-ML electronic states at a weak interfacial interaction. Furthermore, first-principles calculation clearly demonstrates the interfacial rearrangement. These results provide evidence that the rearrangement of orbital energies, which is realized in HOMO–LUMO and HOMO–HOMO−1 gaps, brings partially occupied LUMO through the surface-induced aromatic stabilization of DIP, a pure hydrocarbon molecule, on Cu(111).
Peptide-based molecular electronic devices are promising due to the large diversity and unique electronic properties of biomolecules. These electronic properties can change considerably with peptide structure, allowing diverse design possibilities. In this work, we explore the effect of the side-chain of the peptide on its electronic properties, by using both experimental and computational tools to detect the electronic energy levels of two model peptides. The peptides include 2Ala and 2Trp as well as their 3-mercaptopropionic acid linker which is used to form monolayers on an Au surface. Specifically, we compare experimental ultraviolet photoemission spectroscopy measurements with density functional theory based computational results. By analyzing differences in frontier energy levels and molecular orbitals between peptides in gas-phase and in a monolayer on gold, we find that the electronic properties of the peptide side-chain are maintained during binding of the peptide to the gold substrate. This indicates that the energy barrier for the peptide electron transport can be tuned by the amino acid compositions, which suggests a route for structural design of peptide-based electronic devices.
Angle-resolved and -integrated photoemission spectra from the ZnSe(110) surface were measured with He I (21.2 eV) light. Angle-resolved spectra were taken for the ? -?′, ? -?, and ? -? symmetry lines. From oxygen-contamination tests and by comparing the experimental result with a calculated surface electronic structure, we expect both surface and bulk states to contribute to the emission spectrum. The dispersion of the surface states at ∠−1.0 eV (energy zero is taken at the valence-band maximum) near the ?′ point and at ∠−1.5 eV near the ? point are reproduced by the calculation, while the presence of the surface state at −4 eV near the ? point is not predicted by the calculation. The Se-s-like surface state is detected at ∠0.5–1.0 eV above the upper edge of the lower valence band. The emission features due to valence-band states are interpreted by a model which disregards conservation of the wave vector perpendicular to the surface. The energies of the valence-band states at the X, W, and L critical points are determined: X5 = −2.5, X3 = −5.25, W2 = −3.4, W1 = −5.1, and L1 = −5.7 eV.
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