3 research outputs found
Evidence of Hybrid Excitons in Weakly Interacting Nanopeapods
Nanopeapods, consisting of optically
active π-conjugated
molecules encapsulated inside of the cavity of carbon nanotubes, exhibit
efficient photon emission in the visible spectral range. Combining
optical experiments with ab initio theory, we show that the puzzling
features observed in photoluminescence spectra are of excitonic nature.
The subunits though being van der Waals bound are demonstrated to
interact in the excited state, giving rise to the formation of hybrid
excitons. We rationalize why this many-body effect makes such nanohybrids
useful for optoelectronic devices
Epitaxy of Rodlike Organic Molecules on Sheet SilicatesA Growth Model Based on Experiments and Simulations
During the last years, self-assembled organic nanostructures have been recognized as a proper fundament for several electrical and optical applications. In particular, phenylenes deposited on muscovite mica have turned out to be an outstanding material combination. They tend to align parallel to each other forming needlelike structures. In that way, they provide the key for macroscopic highly polarized emission, waveguiding, and lasing. The resulting anisotropy has been interpreted so far by an induced dipole originating from the muscovite mica substrate. Based on a combined experimental and theoretical approach, we present an alternative growth model being able to explain molecular adsorption on sheet silicates in terms of molecule−surface interactions only. By a comprehensive comparison between experiments and simulations, we demonstrate that geometrical changes in the substrate surface or molecule lead to different molecular adsorption geometries and needle directions which can be predicted by our growth model
Epitaxial Growth of π‑Stacked Perfluoropentacene on Graphene-Coated Quartz
Chemical-vapor-deposited large-area graphene is employed as the coating of transparent substrates for the growth of the prototypical organic n-type semiconductor perfluoropentacene (PFP). The graphene coating is found to cause face-on growth of PFP in a yet unknown substrate-mediated polymorph, which is solved by combining grazing-incidence X-ray diffraction with theoretical structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and “standing” films, we report a π-stacked arrangement of coplanar molecules in “flat-lying” films, which exhibit an exceedingly low π-stacking distance of only 3.07 Å, giving rise to significant electronic band dispersion along the π-stacking direction, as evidenced by ultraviolet photoelectron spectroscopy. Our study underlines the high potential of graphene for use as a transparent electrode in (opto-)electronic applications, where optimized vertical transport through flat-lying conjugated organic molecules is desired