Self-Assembly of Tetraphenyldibenzoperiflanthene (DBP) Films on Ag(111) in the Monolayer Regime

Abstract

Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light-emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained, and their mutual alignment was characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution, resembling the shape of the frontier orbitals in the gas phase as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces do not form highly ordered aggregates.

Hybridization vs decoupling: influence of an h-BN interlayer on the physical properties of a lander-type molecule on Ni(111)

“…A comparison with reported lateral structures of DBP on Ag(111) [ 34 ] and Au(111) [ 33 ] shows very similar adsorbate lattice parameters except for the unit cell rotation with respect to the primitive substrate vector (see Table 1 ). For this reason, we find that the molecules adopt a similar herringbone arrangement (rectangular unit cell with a basis of two molecules with different azimuthal orientation) on h-BN/Ni(111).…”

“…In the case of highly ordered DBP on h-BN/ Ni(111), suitable coincidences with the lowest substrate orders are the on-line coincidences (1, 2), (−1, −2), (−2, 1), and (2, −1). [34]. The angle Γ is defined between the lattice vectors of the adsorbate and .…”

Exciting vibrons in both frontier orbitals of a single hydrocarbon molecule on graphene

“…An important prerequisite for vibrational progression to occur is the presence of sharp molecular resonances and, thus, the extended lifetime of the transient charge state of the molecule [54], which is fulfilled here owing to the weak DBP-metal hybridization [39,55]. The peaks n ± (n ≥ 1) are not due to other molecular orbitals since calculations of the free molecule revealed that the HOMO−1 (LUMO+1) is 1 eV below (above) the HOMO (LUMO) energy [53].…”

Fano Description of Single-Hydrocarbon Fluorescence Excited by a Scanning Tunneling Microscope

“…The optimized structure was obtained by density functional calculations at the B3LYP/6 − 311G++(d,p) level. 44 The energy of the weak fluorescence peak at 2.28 eV (ε), which was not reported in the absorption experiments, 45 is compatible with light emission from non-thermalized excitons, a photon emission process that is generally referred to as hot electroluminescence where vibrationally excited states of S 1 relax to the vibrational ground state of S 0 , i. e., The Purcell effect (vide supra) entails a strong reduction of the fluorescence lifetime in plasmonic environments. Similar observations of luminescence peaks blue-shifted from the S 1 (ν = 0) −→ S 0 (ν = 0) transition were reported from multilayers of phthalocyanines 21…”