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DS: Fachverband Dünne Schichten

DS 44: Postersession II

DS 44.3: Poster

Donnerstag, 23. März 2017, 17:00–19:00, P1C

Photo absorption of adsorbed azobenzene monolayers: impact of graphene substrate — •Qiang Fu, Caterina Cocchi, Dmitrii Nabok, Andris Gulans, and Claudia Draxl — Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany

To reveal the impact of a graphene substrate on the photo-absorption of azobenzene (AB), we investigate the optical spectra of both isolated and adsorbed AB monolayers within the framework of density-functional theory (DFT) and many-body perturbation theory (MBPT), as implemented in the full-potential all-electron code exciting [1]. In spite of weak hybridization, the optical excitations of AB monolayers are remarkably modulated. The excitation energies are affected via two counteracting mechanisms: Substrate polarization reduces the band-gap of the adsorbate, and enhanced dielectric screening weakens the attractive interaction between electrons and holes. The competition of the two effects give rise to a blueshift of peaks from intramolecular excitations and a redshift of peaks from intermolecular ones. Excitations corresponding to intermolecular electron-hole pairs, which are dark in the isolated AB monolayers, are activated by the presence of graphene. Our results demonstrate that the photoswitching property of weakly adsorbed azobenzene undergoes notable changes on a carbon-based substrate.

[1] A. Gulans et al., J. Phys.: Condens. Matter 26, 363202 (2014).