Recent Achievements



Organic/polymer transistors can enable the fabrication of large-area mechanically-flexible electronic circuits and systems. In this regard, thermal evaporation through low-resolution shadow masks is a promising technological solution for the low-cost mass production of flexible circuits. However, organic devices are inherently temperature sensitive due to the strong temperature dependence of their charge carrier mobility, suffer from low thermal conductivity of plastic substrates, and are slow due to the low charge carrier mobility and long channel length.


A paper recently published in ACS Nano by cfaed members has been presented as Research Highlights in Nature Materials.
The work by Robin Ohmann, Jörg Meyer, Anja Nickel, Jorge Echeverria, Maricarmen Grisolia, Christian Joachim, Francesca Moresco, Gianaurelio Cuniberti with the title “Supramolecular Rotor and Translator at Work: On-Surface Movement of Single Atoms” describes how an electronically driven supramolecular structure can generate work by moving atomic-size loads.

The abstract reads as follows: A supramolecular nanostructure composed of four 4 acetylbiphenyl molecules and self-assembled on Au (111) was loaded with single Au adatoms and studied by scanning tunneling microscopy at low temperature. By applying voltage pulses to the supramolecular structure, the loaded Au atoms can be rotated and translated in a controlled manner. The manipulation of the gold adatoms is driven neither by mechanical interaction nor by direct electronic excitation. At the electronic resonance and driven by the tunneling current intensity, the supramolecular nanostructure performs a small amount of work of about 8 x 10-21 J, while transporting the single Au atom from one adsorption site to the next. Using the measured average excitation time necessary to induce the movement, we determine the mechanical motive power of the device, yielding about 3 x 10-21 W.

controlled transport of single atoms by an electronically driven molecular nanostructure


By using vertical current transport and thin organic layers, these devices allow for low operation voltages and high current densities without the need for active structuring. First devices exhibiting a transmission of 99% and an amplification of over 1000 have been realized.

First very interesting results on new materials for OFETs have been shown by the Voit group. In next steps, mobility characterization experiments will be performed and first transistors with these new materials will be built by the Leo group.

Details of very important achievements of the group are listed below:

  • Synthesis of new, all-conjugated block copolymers, first time by Kumada coupling; oxy-gen-stable; publication in preparation;
  • Synthesis of monomer for high-mobility polymers (6g), first successful polymerization;
  • Synthesis of various polymers as gate dielectrics; studied in device structures, joint publication in preparation;
  • Synthesis of high refractive index polymers, studied in OLED systems, one publication submitted, joint publication in preparation;
  • Synthesis of new liquid-crystalline dielectrics as gate dielectric, study of dielectric and breakthrough properties, joint publication in preparation.

The group of Prof. Ellinger realized the first fully printed organic amplifier within the matching fund project FLEXIBILITY in cooperation with Organic Path. They demonstrated a TFT operational amplifier on plastic with 23 dB gain and only 160 µW dc power within the matching fund project FLEXIBILITY in cooperation with Organic Path. They realized a compact TFT model developed within the matching fund project FLEXIBILITY in cooperation with Organic Path. They demonstrated a 2.62 MHz 762 µW Cascode Amplifier in Flexible a-IGZO Thin-Film Technology for Textile and Wearable-Electronics Applications within the matching fund project FLEXIBILITY in cooperation with Organic Path. The group successfully cooperates with Prof. Fischer (Polymer technology and devices) and Prof. Hübler (printing technologies).

New dopants for OLEDs have been synthetized by the group of F. Moresco and characterized on the Au(111) surface by scanning tunneling microscopy and spectroscopy to determine their adsorption properties and their electronic structure.


  • Publication in Nature Communications: ‘Doped Organic Transistors: Inversion and Depletion Regime’, by B. Lüssem, K. Leo et al.
  • Best Poster prize was awarded to Tim Erdmann at ISSON13 - 7th International Summer School on Nanosciences & Nanotechnologies (Thessaloniki, Greece, 6.-13. July 2013) for the poster: The first chain-growth polymerization of a dithienosilole monomer and new all-conjugated block copolymers for plastic electronics
  • R. Brückner was awarded the Goldberg-Prize for an outstanding dissertation (Robert-Luther-Foundation, TU Dresden, 2014)


Combing polymers for better organic solar cells

After we previously demonstrated, that controlling the ink-flow with our FLUENCE technique leads to massive improvements in the film structure and performance for small organic semiconductor inks, a new paper, published in Nature Communications, describes our modification of the FLUENCE approach to work with conjugated semiconducting polymers.
The question here was: can we achieve similar control over the morphology of polymer films as we achieved for the small molecules. The answer is yes, but in order to work for polymers, the structures controlling the ink flow needed to be shrunk from tens of micrometers down to as small as possible. New shearing blades with photo-lithographic structured pillars of 1-2 micrometer diameter and pitch were produced. These specially structured blades improved the morphology of printed polymer films for organic solar cells and enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation.


Follow some coverage that the research on “Nano grass” for organic photovoltaic devices recently received. This work is the result of a collaboration with Prof. Briseno, UMass, USA.

nano grass