Regensburg 2016 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 56: Organic-Inorganic Systems III: Electronic Structure (organized by O)

CPP 56.8: Talk

Thursday, March 10, 2016, 17:00–17:15, S051

Nanoscale Imaging of Charge Carrier and Exciton Trapping at Structural Defects in C₆₀ Films — •Christoph Große¹, Olle Gunnarsson¹, Pablo Merino¹, Klaus Kuhnke¹, and Klaus Kern^1,2 — ¹Max-Planck-Institut fürr Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany — ²École Polytechnique Fèdérale de Lausanne, 1015 Lausanne, Switzerland

Charge carrier and exciton trapping in organic semiconductors crucially determine the performance of organic (opto-) electronic devices, such as organic field-effect transistors, light-emitting diodes, or solar cells. However, the microscopic origin of the relevant traps generally remains unclear, as most spectroscopic techniques are unable to probe the electronic structure of individual traps and the morphological structure causing them. Here, we employ low-temperature scanning tunneling microscopy (STM) and tunneling spectroscopy as well as tight-binding calculations derived from ab initio calculations to image the localized electronic states arising at structural defects in thin C₆₀ films (<10 ML). The spatially and spectrally resolved STM-induced luminescence at these states reveals an enhanced radiative decay of excitons, which is interpreted in terms of the local symmetry lowering and the trapping of excitons by an X-traps. The combined mapping of the STM-induced luminescence, electronic structure, and morphology thus provides new insights into the origin and characteristics of individual exciton traps in organic semiconductors and opens new avenues to study charge carrier and exciton dynamics at molecular scales.