Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 45: Organic-Inorganic Hybrid Systems and Organic Films

O 45.5: Poster

Tuesday, March 21, 2017, 18:30–20:30, P1A

How K-doping affects the properties of DBP monolayers on Ag(111) — •Tino Kirchhuebel, Felix Otto, Marco Gruenewald, Roman Forker, and Torsten Fritz — Institute of Solid State Physics, Friedrich Schiller University Jena, Germany

Doping is a suitable tool to tune the electronic properties and the absorption of organic semiconductors for the purpose of specific technical applications. Recently, tetraphenyldibenzoperiflanthene (DBP), which is applicable as a donor or acceptor for other molecules,¹ was used as a component of optoelectronic devices. Here, we investigate how doping affects DBP itself, by studying the interplay between the optical and electronic properties, as well as the structure of potassium doped epitaxial DBP thin films on Ag(111). For DBP sub-monolayers several different laterally ordered structures depending on the local K:DBP stoichiometry are observed using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). As concluded from ultraviolet photoelectron spectroscopy (UPS) experiments, an electron transfer from potassium to DBP is achieved. Our differential reflectance spectroscopy (DRS) measurements show that this lowest unoccupied molecular orbital (LUMO) filling leads to tremendous alterations of the molecular absorption and even reduces the molecule-substrate interactions significantly. The optical fingerprints of DBP anions with reduced hybridization to the silver surface and dianions, which are rather effectively decoupled from the substrate, are identified by comparison to optical spectra of K-doped DBP films on inert mica.
[ 1] A. N. Bartynski et al., J. Phys. Chem. C, 2016, 120 , 19027.