NEXT GENERATION MATERIALS
Developing tailor-made materials for organic electronics for solution processes like printing by feeding back insight from processability studies into synthesis.
Heidelberg University (OCI)
At InnovationLab, young researchers from the Institute of Organic Chemistry (Masters / PhD students and postdocs) work hand in hand with researchers from various disciplines and industries in the field of synthesis.
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, the latest device performance data are utilized to immediately improve the next generation materials. This way, feedback 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.
- solubility switching materials
- surface modification
- printable silver inks
- novel organic dopants
- new semiconductor structures
Through close cooperation between the competence centers, a large variety of projects are currently worked on. Several projects where synthesis is involved can be found in this diagram.
Solubility Modulation of 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 subsequent 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 a stimulus, either via cross-linking, a precursor route, or removal of solubilizing groups. 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 Interfaces
Within the Competence Center Synthesis molecules and means are developed to modify inter- and surfaces that commonly occur 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 (FKZ 13N11701) by the BMBF.
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 competence 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 bulk and at the interfaces.
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 the 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.
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 behavior in, e.g. bulk heterojunctions, together with the Competence Center Analytics and Simulation. The aim of our work is to develop 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).
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 look at innovative ways 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.
If organic semiconductors are to be processed from the solution, the 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 possibility to improve the contact between inorganic substrates (e.g. ITO) and organic functional materials is the application of a thin, conductive organic layer on top. An established method to do this is to spin-coat doped polymers (like PEDOT:PSS in water) onto the substrate. An interesting alternative is electropolymerization: The conductive material is directly produced on 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.
In addition, we are using the following equipment:
Thermogravimetric Analysis/Dynamic Differential Calorimetry
Combined TGA/DSC-System by Mettler-Toledo
Irrespective of the 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/Galvanostat by Princeton Applied Research
To perform electropolymerisations and for the 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.
Laboratory Centrifuge by Sigma
Used to purify semiconducting polymers by precipitation.
Microwave Reactor by Anton Paar
For efficient and homogeneous heating of reaction solutions as well as performing reactions under slight overpressure.
Automated Purification System by Biotage
For repeated purification of important intermediates on a larger scale.
Rainer Bäuerle, M.Sc.
Study Group Prof. Dr. Uwe H. F. Bunz
Research Project 2 HORISONS
Pariya Nazari, M.Sc.
Study Group Prof. Dr. Uwe H. F. Bunz
Research Project 2 HORISONS