Regensburg 2019 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 16: Organic Thin Films, Organic-Inorganic Interfaces

DS 16.11: Vortrag

Mittwoch, 3. April 2019, 12:15–12:30, H39

Switching the surface electronic properties of polar ZnO crystals with photochromic pyridyl-dihydropyrene molecular layers — •Qiankun Wang¹, Giovanni Ligorio¹, Raphael Schlesinger¹, Valentin Diez-Cabanes², David Cornil², Yves Garmshausen¹, Stefan Hecht¹, Jérôme Cornil², Emil J. W. List-Kratochvil¹, and Norbert Koch¹ — ¹Humboldt-Universität zu Berlin — ²University of Mons

Remote control of the electronic energy levels by external stimuli such as light will enable optoelectronic devices with improved or additional functionalities. Here, we demonstrate that the electronic properties of ZnO interfaced with molecular negative T-type photoswitches, i.e., pyridyl-dihydropyrene (Py-DHP), can indeed be photomodulated. Using photoemission spectroscopy and density functional theory (DFT) modelling, we show that the photochromic ring closure/opening process results in reversible shift of the frontier occupied molecular level by 0.7 eV with respect to the Fermi level. Notably, in both molecular configurations, the energy level alignment at the ZnO/Py-DHP interface is governed by a Fermi level pinning of the lowest unoccupied molecular level. Moreover, upon switching, we observe an increase in the ionization energy for Py-DHP multilayers compared to that of a monolayer. We attribute this to a different preferred molecular orientation in monolayer versus multilayer films. Our results show that dynamic tuning of the interface energy level alignment at inorganic/organic junctions by external stimuli is indeed possible and will aid the development of photoprogrammable opto-electronic devices.