Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 89: Inorganic/Organic Interfaces: Molecular Switches

O 89.2: Talk

Thursday, March 19, 2015, 15:15–15:30, MA 043

Excited-State Properties of Azobenzene Self-Assembled Monolayers from Many-Body Perturbation Theory — •Caterina Cocchi and Claudia Draxl — Physics Department and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany

Self-assembled monolayers (SAMs) of azobenzene-functionalized alkanethiols on gold exhibit remarkable intermolecular interactions in the excited state [1]. Excitonic coupling plays a crucial role in quenching the trans/cis photo-isomerization in the SAMs, compared to single molecules. We perform an in-depth first-principles study of the excited-state properties of the chromophore SAMs. In the framework of density-functional and many-body perturbation theory, as implemented in the all-electron full-potential code exciting [2], we investigate optical and core-level excitations of azobenzene SAMs, functionalized with different end groups. By analyzing the character of the electron-hole pairs, systematically going from the constituent molecules to SAMs of increasing density, we identify the fingerprints of the backbone structures and those of the functional groups. Our results represent an important step forward to interpret available experiments [1], and to gain insight into the microscopic mechanisms that rule excited-state isomerization in these materials. [1] C. Gahl et al. J. Am. Chem. Soc. 132, 1838 (2010). [2] A. Gulans et al. J. Phys.: Condens. Matter 26, 363202 (2014).