Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 46: Poster Organic Molecules on Inorganic Substrates: Electronic, Optical and Other Properties

O 46.1: Poster

Dienstag, 18. März 2025, 18:00–20:00, P2

Electronic Properties of Interfaces between N-Heterotriangulene Donors and Strong Tetracyanoquinodimethane Acceptors — •Mohsen Ajdari¹, Jakob Roth¹, Ronja Pappenberger¹, Christian Walla², Ina Michalsky³, Friedrich Maaß¹, Milan Kivala³, Andreas Dreuw², and Petra Tegeder¹ — ¹Physikalisch-Chemisches Institut — ²Interdisziplinäres Zentrum für Wissenschaftliches Rechnen — ³Organisch-Chemisches Institut, Heidelberg University

N-Heterotriangulenes (N-HTAs) are promising functional molecules with significant potential for optoelectronic applications, in particular, as electron donors in donor/acceptor (D/A) systems. This study explores the electron-donating properties of two N-HTAs, N-HTA 550 and N-HTA 557, at interfaces with well-known tetracyanoquinodimethane acceptors, TCNQ and F4TCNQ. Using high-resolution electron energy loss spectroscopy (HREELS) combined with quantum chemical calculations, we investigated the electronic properties of D/A interfaces adsorbed on Au(111) [1]. For all D/A combinations, low-energy electronic transitions (E<2.5 eV) associated with charge transfer (CT) states are identified. Quantum chemical calculations rule out the formation of ground-state CT complexes. Instead, CT in the excited state, in which an electron-stimulated CT from the N-HTAs to TCNQs is the underlying process, is proposed. The energies of the CT states are determined by the values of the ionization potential and electron affinity of the involved donor and acceptor.
[1] M. Ajdari et al., J. Phys. Chem. C, 128, 14399-14406 (2024)

Keywords: N-heterotriangulenes; high-resolution electron energy loss spectroscopy; charge transfer at D/A interfaces