Dresden 2026 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 12: Scanning probe microscopy: light matter interaction at atomic scales
O 12.1: Vortrag
Montag, 9. März 2026, 15:00–15:15, HSZ/0403
Upconversion electroluminescence in VOPc via adsorption-induced interaction of unpaired spin — •Lukas Gerhard1, Vibhuti Rai1, Christof Holzer1, Carsten Rockstuhl2, and Wulf Wulfhekel1 — 1Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen, Germany — 2Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany
Molecules with unpaired spins (radicals) promise favourable spin statistics in their electroluminescence. Here, we combine scanning tunneling microscopy induced luminescence and density functional theory to study single vanadyl phthalocyanine molecules, which are stable neutral radicals. Two distinct adsorption geometries of the molecule on NaCl/Au(111) lead to a difference in the interaction of the unpaired electron with the substrate, which in turn allows us to investigate its effects on the light emission process [1]. Remarkably, we observe that up-conversion electroluminescence is gated by the adsorption geometry of the molecule, an effect we attribute to a reordering of excited states and enhanced excited state transition probabilities. The profound influence of the unpaired electron via state reordering opens new possibilities for tuning not only molecular electroluminescence but also many other spin dependent phenomena.
[1] V. N. Rai, C. Holzer, C. Rockstuhl, W. Wulfhekel, and L. Gerhard, arXiv:2508.11501.
Keywords: STML; up-conversion electroluminescence; unpaired spin; state reordering