Frank Ortmann Group News

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

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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.

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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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Festive inauguration of the new building for the Center for Advancing Electronics Dresden (cfaed)

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Handing over the "key" for the new building, symbolized by a doped C60 molecule. Some inspiration might have come from our Nature Mater. paper :-)

Today, Dr. Matthias Haß, Minister of Finance, and Dr. Eva-Maria Stange, Minister of Science, handed over the keys to the cfaed Cluster of Excellence facilities in the Barkhausen building to the Rector of TU Dresden, Prof. Hans Müller-Steinhagen. The opening of the new TU Dresden building enables the cluster to bring together a large number of researchers in one location. Also our group has moved in recently.
The design of the office spaces and the highly sophisticated laboratories not only creates a single space for collaborative research, but the new building itself is located in the immediate vicinity of the Andreas-Pfitzmann building, the Hermann-Krone building and the adjacent institutes and departments that are of crucial importance to the cfaed. The Faculty of Electrical and Computer Engineering, the Faculty of Computer Science and the Faculty of Mechanical Science and Engineering as well as the School of Science have their main facilities right next door. Interdisciplinary research requires physical proximity and effective communication: this is precisely what the new building offers to cfaed.

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Investigating the Doping of Organic Semiconductors: Research Group at the Center for Advancing Electronics Dresden (cfaed) Simulates Doping Mechanism

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Geometry of a molecular cluster of dopant and host molecules with benzimidazoline dopant and a C60 molecule (ball and stick model; atoms are indicated in blue (N), dark grey (C) and light grey (H)) surrounded by C60 molecules (stick model). Credit: S. Schellhammer/ F. Ortmann

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A group of physicists from the cfaed at TU Dresden, together with researchers from Japan, were able to demonstrate in a study how the doping of organic semiconductors can be simulated and experimentally verified. The study has now been published in “Nature Materials”.

In semiconductor technology, doping refers to the intentional introduction of impurities (also known as dopants) into a layer or into the intrinsic semiconductor of an integrated circuit. These dopants are deliberate modifications of the semiconductor, with which the behavior of the electrons and thus the electrical conductivity of the intrinsic material can be controlled. Even the smallest amounts of dopants can have a strong impact on the electrical conductivity. Electronic modifications by doping make semiconductors functional in all major electronic devices – the backbone of the electronics industry.

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Antonis starts PhD in Cambridge. We wish him all success.

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