Heidelberg University (OCI)

In the competence center Synthesis, early stage researchers from academia (master/PhD students and postdocs) work hand-in-hand with researchers from diverse disciplines and industry.

We develop materials utilized in organic electronics enabling large-area solution processes like printing. Feeding back insights from device fabrication processes into synthesis allows for immediate tuning of the material properties.  

By closely cooperating with the other competence centers on-site, latest device performance data are utilized to immediately improve the next generation materials. This way, feed-back loops are sped up and tailor-made materials for solution processing are realized in the labs of the Institute for Organic Chemistry (OCI) of Heidelberg University.

 

 

Research focus:

  • solubility switching materials
  • surface modification
  • printable silver inks
  • novel organic dopants
  • new semiconductor structures


Through close cooperation with the other Competence Centers, a large variety of projects are being worked on. A number of projects where synthesis is involved can be found in this diagram.

Possibilities to Switch Solubility (© M. Hamburger, Heidelberg University)

Solubility Switching Materials

For cost-efficient fabrication of OE-based devices, high-throughput processes like printing are required. However, the fabrication of consecutive layers from solution is challenging, as each layer has to be resistant to the solvent used for the next layer. To process multiple layers from solvents of similar polarity in a controlled fashion, semiconductor materials are modified in the Competence Center Synthesis to reduce their solubility drastically upon an applied external stimulus. Ideally this stimulus can be used to structure the material laterally as well. One important aspect of our work here is the compatibility of stimulus, substrate, semiconductor and processing conditions.

Our work in this field is funded by the Federal Ministry of Education and Research (BMBF) within the POESIE project (FKZ 13N13695). Previous work was funded in the MORPHEUS project (FKZ 13N11701) (Unfortunately, the link is only available in German).

Self-Assembling Monolayers for Modification of Interphases

Improved charge carrier mobility and -injection by surface modification (© M. Hamburger, Heidelberg University)

Within the Competence Center Synthesis molecules and means are developed to modify inter- and surfaces which are commonly encountered in organic electronic devices. The quality of devices often crucially depends on these interfaces. Especially the semiconductor-dielectric interface in field-effect transistors and semiconductor-electrode contact are important. Small conjugated molecules can, as self-assembling monolayers (SAMs), shift the work function of electrodes to achieve better alignment with the organic semiconductor as well as to improve the wettability of the surface and thus contact to the semiconductor. We develop new SAM molecules for metal oxides such as ITO and metals such as silver and gold and tune size and orientation of their dipole moments with respect to the surface.

Our work is funded within the Interphase project (FKZ 13N13695) by the BMBF. Previous work was funded within the MORPHEUS project (link auf Steckbrief) (FKZ 13N11701) by the BMBF (Unfortunately, the link is only available in German).

Novel organic dopants

Molecular doping increases conductivity both of organic small molecules and polymers. Ohmic losses in the charge transport layers and injection barriers at interfaces to electrodes can be drastically reduced. P- and n-type dopants are synthesized in the Comptence Center and tested with respect to air/moisture stability as well as solubility and their doping strength to achieve more soluble materials of higher potency compared to literature. Doping effects are studied in mixed phases and at interlayers.
Our work is funded within the Interphase project (FKZ 13N13695) by the BMBF.
Printable silver inks
Fully solution processed devices require printable electrode materials. Silver electrodes can be obtained after sintering of the respective nanoparticles. In order to stabilize them in solution, we develop stabilized nanoparticles allowing for low sintering temperatures and study them together with the Competence Centers Printing and Analytics.

Our work is funded within the POESIE project (FKZ 13N13695) by the BMBF.

Novel Semiconductors

Electron-transporting materials are needed for a wide range of devices and ideally should be insensitive to air and humidity.Within the Competence Center Synthesis, we develop new acceptor structures and study their stability and phase behaviour in e.g. bulk heterojunctions together with the Competence Center Analytics and Simulation. Aim of our work are materials for electron-transporting layers in OLEDs, for n-channel transistors in complementary circuits and acceptors in organic solar cells.
Our work on new acceptor structures was funded by the BMBF (FKZ 13N11701).

Former projects:

Printed organic thermoelectric generators

Thermoelectric generators (TEGs) produce electrical energy from a temperature difference. Organic TEGs offer unique opportunities, especially with respect to large-area processing techniques like printing, allowing for mass production of devices.

In the field of organic thermoelectric materials, doped PEDOT-derivatives are the reference material in terms of conductivity and stability. The efficiency of a PEDOT-based TEG can be improved by suitable processing. We investigate means to improve the processability and performance of these materials even further.
 
Our work in this field was done within the research alliance HEiKA within the project PEDOT2.0 together with the Light Technology Institute of the KIT.

ELPOLITO

Electropolymerised PEDOT and its wetting properties (© M. Hamburger, Heidelberg University)

If organic semiconductors are to be processed from solution, wettability of the substrate is a key issue. The surface tension of the fluid and the surface energy of the substrate have to be matched. One opportunity to improve the contact between inorganic substrates (e.g. ITO) with organic functional materials is preparation of a thin, conductive organic layer on top. One established method to do so is to spin-coat doped polymers (like PEDOT:PSS in water) onto the substrate. One interesting alternative is electropolymerisation: The conductive material is directly prepared onto the surface in question.
 
This project was funded by Heidelberg University within the Central Research Pool.
 

Besides state-of-the-art laboratories for chemical synthesis, we have acces to the infrastructure of the Institute of Organic Chemistry at Heidelberg University.

Additionally we are using the following equipment:

Thermogravimetric analysis / dynamic differential calorimetry

Combined TGA/DSC-System by Mettler-Toledo
 
No matter which processing technique (physical vapor deposition or solution processing) thermal stability and phase behavior of organic materials are important parameters to know.
 
These can be measured using TGA/DSC.

 

Potentiostat/Cyclic voltammetry

Potentiostat/Galvanostat by Princeton Applied Research
 
To perform electropolymerisations and for analysis of redox potentials of new materials via cyclic voltammetry we use this potentiostat.

 

T4-Glovebox with freezer

T4-Glovebox with Freezer by Glovebox Systemtechnik

For handling air- and moisture-sensitive compounds, we use this glovebox.

 

Centrifuge

Laboratory Centrifuge by Sigma

To purify semiconducting polymers by precipitation.

 

Microwave reactor

Microwave Reactor by Anton Paar

For efficient and homogeneous heating of reactions as well as performing reactions under slight overpressure.

 

Purification system

Automated Purification System by Biotage
 
For repeated purification of intermediates on a larger scale.

PhD Students

Ali Abdulkarim

PhD student
contact via email
Room: INF 270 R.0.112
Phone: +49 (0) 6221 54 64 38 (OCI)

Maximilian Ackermann

PhD student
contact via email
Room: INF 271 R.0.18
Phone: +49 (0) 6221 54 85 71 (OCI)

Simon Benneckendorf

PhD student
contact via email
Room: INF 270 R.0.112
Phone: +49 (0) 6221 54 64 38 (OCI)

Gérard Bollmann

PhD student
contact via email
Room: INF 271 R.0.18
Phone: +49 (0) 6221 54 85 71 (OCI)

Manuela Casutt

PhD student
contact via email
Room: INF 271 R.2.11
Phone: +49 (0) 6221 54 61 47 (OCI)

Master & Bachelor

Lukas Ahrens

Master student
contact via email
Room: INF 271 R.2.11
Phone: +49 (0) 6221 54 61 47 (OCI)

Nico Balzer

Master student
contact via email
Room: INF 270 R.112
Phone: +49 (0) 6221 54 64 38 (OCI)

Nadja Klipfel

Master student
contact via email
Room: INF 271 R.0.18
Phone: +49 (0) 6221 54 85 71 (OCI)

Alumni

  • Dr. Florian Golling (former group head)
  • Dr. Manuel Hamburger (former group head)
  • Dr. Felix Hinkel (former group head)

  • Silas Aslan, M.Sc.
  • Dr. Malte Jesper
  • Dr. Marius Kuhn
  • Dr. Torben Peters
  • Dr. Martin Petzoldt
  • Maik Rudloff, M.Sc.
  • Dr. Korwin Schelkle
  • Artur Schneider, M.Sc.
  • Dr. Claudia Teusch
  • Svenja Taschinski, M.Sc.