Frank Ortmann Group News

Professorship for Frank Ortmann at TU München

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Frank is starting at TU München as Professor for Theoretical Methods in Spectroscopy.

On the trail of organic solar cells’ efficiency: Molecular vibrations reduce the maximum achievable photovoltage in organic solar cells

PRESS RELEASE from cfaed @ TU Dresden, March 20, 2020

Published on in FRANK ORTMANN GROUP

Illustration of the generation of charge pairs (excitons), the precursors of free charge carriers in the active layer of an organic solar cell. Credit: M. Panhans

Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials. Currently, the voltage of such cells is still too low - one reason for their still relatively low efficiencies. In their study, by investigating the vibrations of the molecules in the thin films, the scientists were able to show that very fundamental quantum effects, so-called zero point vibrations, can make a significant contribution to voltage losses. The study has now been published in the journal Nature Communications.

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Tuning the Energy Levels of Organic Semiconductors

Press Release from 04 July, 2019

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Examples of film structures used for the calculations of the charge - quadrupole interaction energy (EQ) of crystalline films in edge-on (a) and face-on orientation (b). The molecules are represented by discs for illustration purpose. The length scale is given in Å. EQ values are calculated for the red molecules at the film surface. Author: Frank Ortmann

Physicists from the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and the Center for Advancing Electronics Dresden (cfaed) at the TU Dresden, together with researchers from Tübingen, Potsdam and Mainz were able to demonstrate how electronic energies in organic semiconductor films can be tuned by electrostatic forces. A diverse set of experiments supported by simulations were able to rationalize the effect of specific electrostatic forces exerted by the molecular building blocks on charge carriers. The study was published recently in Nature Communications.

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Marcus Regime in Organic Devices: Interfacial Charge Transfer Mechanism Verified

Published on in FRANK ORTMANN GROUP

Device schematics. a – Schematic cross section of the device. b – Hot-electron transistor operation. Electrons are injected by applying a negative emitter-base bias, and detected in the molecular semiconductor. These electrons are out of equilibrium with the thermal electrons in the base which cannot be described by a larger temperature. The measurements can be performed either without or with externally applied collector-base bias.

[Deutsche Version unter "read more"]

Physicists from the Research Cluster Center for Advancing Electronics Dresden (cfaed) of the TU Dresden, together with researchers from Spain, Belgium and Germany, were able to show in a study how electrons behave in their injection into organic semiconductor films. Simulations and experiments clearly identified different transport regimes. The study was published now in Nature Communications.

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Shared Vision for Teaching

Lecture series of cfaed, IAPP and IFW researchers on fundamentals of charge carrier transport and related phenomena

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The lecture series Selected Topics on Charge Carrier Transport in Organic Semiconductors starts with lecturers from TU Dresden and the Leibniz Institute for Solid State and Materials Research (IFW Dresden). Frank Ortmann (cfaed) today presents an introduction to Transport in Organic Semiconductors from a theoretical point of view. The aim of this course is to combine the experience of various experts from Dresden in this field and to pass the knowledge on to students and doctoral students.

Researchers at TU Dresden Make Breakthrough in Understanding Electrical Conductivity in Doped Organic Semiconductors

Results have just been published in the renowned journal "Nature Materials"

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Press picture: Illustration of an organic semiconductor layer (green molecules) with dopant molecule (purple). (C): Sebastian Hutsch, Frank Ortmann

Researchers from the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and the Center for Advancing Electronics Dresden (cfaed) at TU Dresden, in cooperation with Stanford University (USA) and the Institute for Molecular Science in Okazaki (Japan), have identified the key parameters that influence electrical conductivity in doped organic conductors.

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