GRK 2948 - Mixed Ionic-Electronic Transport: From Fundamentals to Applications

3D Printing Mixed Conducting Polymers

3D printing technologies have enabled us with the possibility to create highly customized, complex, and functional objects with greater efficiency and precision than traditional manufacturing methods. The investigation of new functional printable materials is crucial for their successful integration in real-life applications. In particular, ionic and electronic conductive materials are highly desirable for many applications including electronics, sensing or energy storage. In this project we will explore new mixed conducting polymers suitable for light based 3D printing. Functional monomers containing electro-active and/or ionic groups will be synthesized and optimized in formulations for 3D printing. Special attention will be paid to transferring the desired functionality to the 3D printed structures. We further aim to apply this approach for the fabrication of functional devices in collaboration with other groups of the RTG.

This project requires a background in organic (and polymer) chemistry and materials science. It involves synthesis and characterization of functional polymers as well as light-based 3D printing and microscopy techniques. Experience with 3D modelling is advantageous.

New Photocrosslinkable Polymer Architectures with Mixed Ion-Electronic Transport

Light is a very versatile tool for synthesis because it can be used to initiate a wide range of chemical reactions, such as photocrosslinking, with high selectivity and efficiency. The advantage of using light is the addition of spatial control to the fabrication process opening new possibilities for structuring of the polymers. In this project, we will investigate the influence of the photocroslinking in the ionic and charge transport as well the polymer architecture (e.g. linear (co)polymers vs brushes or star polymers). To this aim, a library of polymers decorated with redox as well as photocrosslinkable units exhibiting different architecture will be synthesized. An in-depth characterization of the generated materials will be carried out in collaboration with other groups of the RTG.

This project requires a background in organic (and polymer) chemistry and materials science. It involves polymer synthesis, light irradiation set-ups and advanced characterization techniques.

  • Main Advisor: Prof. Dr. Eva Blasco
  • Research Group Website:https://www.imseam.uni-heidelberg.de/blasco
  • Location/Institute:Heidelberg University, Institute of Molecular Systems Engineering and Advanced Materials (IMSEAM), Im Neuenheimer Feld 225, Heidelberg

Systematically microengineered conductive hydrogels

Electrically conductive hydrogels are important materials with applications ranging from bioelectronics to cardiac tissue engineering. In this project, we will explore novel strategies for generating microengineered conductive hydrogels based on direct laser writing and electrospinning. We will in particular explore the resolution limits of fabricating conductive hydrogels with the different methods, leading to limits in conductivity and in the function of electrochemical transistors (ECTs), in which the materials will be incorporated. Detailed analysis of the structure-function relationship, e.g., dependency of electrical conductivity on branching of conductive channels and scaling of conductivity with decreasing size of the material, will be explored and strategies for integration in ECTs will be investigated.

This project requires a background in materials science, polymer chemistry or similar. It involves direct laser writing in a cleanroom, electrospinning in a chemistry lab, electrical characterization, and microscopy techniques.

  • Main Advisor: Prof. Dr. Christine Selhuber-Unkel
  • Research Group Website:https://www.imseam.uni-heidelberg.de/selhuber
  • Location/Institute:Heidelberg University, Institute of Molecular Systems Engineering and Advanced Materials (IMSEAM), Im Neuenheimer Feld 225, Heidelberg

Porous Molecules and Polymers for Highly Selective Cation and Anion Binding for Sensing and Transport

Shape-persistent organic cages of defined sizes, geometries with functional groups in the interior or the peripheries can be synthesized in high yields using dynamic covalent chemistry. Furthermore, they can be post-synthetically turned into some more robust compounds by e.g. transforming imine to amide bonds. The tailor-made cages show high selectivities for the recognition of guest molecules, both neutral or charged. Especially selective anion recognition for detection and removal is of interest for environmental (e.g. nitrate) or medical purposes (e.g. chloride).

We will synthesize derivatives of shape-persistent organic cages to create new materials for sensing applications of various anions and cations. For example, the cages will be combined with semiconducting polymers to fabricate electrochemical transistors (ECTs).

This project requires a background in synthetic organic chemistry and/or supramolecular chemistry.

From Advanced Electrochemistry of Tailor-Made Mixed Conducting Polymer Films to Actuating Devices

Two project positions are available in the Ludwigs team which shall focus on mixed ionic-electronic transport of mixed conducting polymers for actuators in soft robotics and switchable organic electrochemical devices.

(1) In-situ Electrochemistry for Actuation: This project will focus on gaining a fundamental understanding of the properties of mixed conducting polymer films using in-situ electrochemical experiments (e.g. in-situ UV-vis, ellipsometry, rheology). Here the main question is how the combination of morphology, doping state and choice of ions affects the films in terms of swelling and reversible switching. For actuator applications high swelling degrees will be targeted. Stimuli will include humidity and electrical fields.

(2) Mixed Conducting Polymer Architectures: A second project will focus on synthetic and film morphology aspects. Here electropolymerization and synthetic post-polymerization strategies such as click chemistry will be pursued. The creation of tailor-made conducting polymer network films will help to develop novel architectures for actuating electrochemical films and devices.

For both projects a chemistry, nano and materials science or physics background is beneficial. The work will involve polymer science, advanced electrochemistry techniques, and morphology and polymer electronics device characterization in a highly interdisciplinary research environment.

Ion and Charge Transport in Nanostructured and Porous SWNT/Polymer-Hybrids for Sensors and Actuators

Semiconducting single-walled carbon nanotubes (SWNTs) can be seen as rolled-up sheets of graphene. They have fascinating optical properties, very high carrier mobilities and can be processed from solution. These characteristics make them highly interesting for novel (opto)electronic devices such as electrochemical transistors. Here, we want to understand and tune the interactions of electrolyte ions with charge carriers in SWNTs, i.e., how ions form electric double layers in the complex environments around polymer-wrapped nanotubes and influence carrier mobility and optical properties (e.g., absorption, emission, scattering). We will explore the impact of the nanotube network structure (from sparse, aligned and dense films to truly three-dimensional) on the ionic and electronic transport in electrochemical transistors with a wide range of electrochemical methods as well as steady-state and time-resolved optical spectroscopies/ microscopies. We further aim to modify and functionalize SWNT networks for application as highly selective chemical sensors and actuators in collaboration with other groups of the RTG.

This project requires a background in physical chemistry, nano- or materials science or experimental physics. It involves solution-based material processing, device fabrication in a cleanroom, electrical characterization, advanced spectroscopy and microscopy techniques.

Advanced Spectroscopies of Local Electronic-Ionic Dynamics in Energy Storage Materials

Design of novel materials for energy storage requires insights on the underlying mechanisms of charge-ion dynamics. A key mechanism is the conversion between delocalized charges and localized ionic species, and their connection to the underlying material, which controls efficiencies and performance of applications. The two available projects will design and employ advanced phase sensitive microscopic spectroscopies for new insights on charge-ion dynamics in real-time and in-operando.

Effects of local environment on charge-ion conversion in hybrid nanostructures

You will use a commercial near-field microscope to reveal the local dielectric function and charging state on sub-100 nm length scales for insights into charging processes at domain boundaries and interfaces of energy materials.

Ultrafast charging dynamics in hybrid battery materials

You will focus on detection of charge conversion and redox processes from ultrafast dynamic of the dielectric function. You will advance concepts for phase-resolved spectroscopies to achieve the sensitivity and time-resolution needed to gain insights into the dynamics of charge storage materials

These projects require a background in physical chemistry, experimental physics or material science. Experience with optical spectroscopy, semiconductors or electro-chemistry is of benefit.

Magnetic probes to study photoactivated processes in mixed ionic-electronic conductors

The project will exploit magnetic probes, i.e., dc/ac magnetisation and electron paramagnetic resonance (EPR), to investigate light- and electrochemically induced ionic and electronic effects. While static magnetic properties provide information on the ground state and are particularly powerful to identify changes between magnetic and non-magnetic oxidation states, EPR is extremely sensitive to discriminate magnetic valence states, to determine the nature and crystalline environment of defects and can provide information of the associated dynamics. In the doctoral project, the experiments will be set-up and feasibility will be demonstrated by studying photo-generated microsecond long-living states in magnetic oxides. Specifically, X-band EPR (dark and illuminated), light-induced SQUID studies, and high-frequency EPR studies will be performed. Furthermore, the experiments will be performed on hybrid organic-inorganic metal-halide perovskites (HOIPs) to investigate the interplay of electronic and ionic transport in collaboration with other groups of the RTG.

This project requires a background in experimental physics with a focus on condensed matter physics and materials properties. Experience in characterising magnetic materials and in magnetic spectroscopy is of advantage.

Mechanisms and applications of ion and dopant motion in organic semiconductors

Using a novel neuromorphic device as testbed system, this project pursues two interconnected goals. First, we will investigate the fundamental mechanisms of dopant and ion motion in organic semiconductors. Depending on the application, this motion should either be slow/absent, e.g. in injection/transport layers and thermoelectrics, or fast, as in sensors or neuromorphic devices. Special emphasis will be put on the largely unexplored but anticipated correlation with electronic motion that would, in the long run, even enable ion pumps. Second, we will develop organic memristive (neuromorphic) devices on basis of novel organic materials coming from collaboration partners. Here, the goal is to control hysteresis in the form of short- and long-term plasticity of the two-terminal conductivity, using dynamic doping by mobile ions.

Apart from being embedded in the Research Training Group on mixed ionic-electronic transport, the candidate will work in a small team that studies doped organic semiconductors using experimental, numerical and theoretical methods

This project involves device fabrication in a cleanroom, advanced electrical characterization and numerical modelling and therefore requires a background in experimental physics or equivalent. Previous experience in a relevant research topic is not essential but desirable.

  • Main Advisor: Prof. Dr. Ir. Martijn Kemerink
  • Research Group Website:https://www.imseam.uni-heidelberg.de/kemerink
  • Location/Institute:Heidelberg University, Institute for Molecular Systems Engineering and Advanced Materials (IMSEAM), Im Neuenheimer Feld 225, D-69120 Heidelberg.

Influence of Ionic and Electronic Transport on the Rheology of Shape Changing Polymeric Materials

Within the project, mixed conductors (e.g., PEDOT:PSS) will be rheologically analyzed through combined uniaxial and torsional experiments. Complex shear and Young’s moduli will be recorded as functions of applied electrical field, temperature and water/electrolyte uptake. The characterization of samples and devices on the scale of millimeters to centimeters will facilitate the investigation of evolving effective elastic moduli (Young’s modulus E and shear modulus G) in harmonic tension and torsion tests while the doping state of the material will be controlled. The coupling of electrical and ionic conductivity with mechanical deformations shall be investigated and volume changes of the material depending on the applied electric field and doping state will be characterized in relation to evolving eigenstrains and eigenstresses. Furthermore, the inverse coupling effect of mechanical actuation on the resulting electronic conductivity is of key interest. The goal is to better understand and predict the emerging rheological properties such as glass transition temperature TG, mechanical relaxation times and materials dissipation of mixed conducting polymers, which have a huge impact on the applicability of these material systems including actuators.
  • Main Advisor: Prof. Dr.-Ing. Holger Steeb
  • Research Group Website:https://www.mib.uni-stuttgart.de/cont/
  • Location/Institute:University of Stuttgart, Institute of Applied Mechanics (MIB), Pfaffenwaldring 7, D-70569 Stuttgart

Molecular modelling of adsorption and transport in swelling, semiconducting porous materials: from ab-initio to coarse-grained simulations

The dynamics of electrochemical doping, bias-induced swelling and the coupled dynamics of (conducting) polymeric systems is highly involved since the doping process also strongly influences ionic, electron and hole mobilities. In this project, we want to address this complex interplay by simulations on multiple length-scales: ab-initio simulations based on density functional theory will provide insight into the interaction between ionic charges and the swelling material. Classical force-field based atomistic simulation including constant potential approaches will be complemented by machine-learned potentials. A full study of swelling phenomena based on the molecular transport coefficients under different humidity, salt concentration and doping conditions will parametrize a coarse-grained model coupled to continuum solvers for hydrodynamic and electrostatic interactions with the electrolyte. This work shall be performed in close collaboration with experimental groups within the RTG that study the swelling and doping dynamics as well as rheological properties.

This project requires a strong background in soft matter simulations, statistical mechanics and thermodynamics. Knowledge of quantum chemistry is encouraged, further background in physical chemistry and machine learning is helpful. The position involves participation in the development of employed software tools like MAICoS1 and ESPResSo2 , thus programming skills in typical languages (Python, C++, …) are beneficial.

Fluctuating hybrid electrokinetic/hydrodynamic description of mixed electronic/ionic transport

The concept of charge carrier hopping is a long-established tool in solid state physics and is successfully applied to transport in semiconductors or to explain transport in solar cells. In the case where an electrolyte solution is in contact with a semiconductor, the dynamics of both the mobile ionic species as well as of electrons and holes is strongly coupled. The aim of this theoretical project is to develop a coupling method that describes simultaneously the coupled ionic/electronic transport based on kinetic Monte Carlo and Molecular Dynamics simulations. On the microscopic site this will be benchmarked against ab-initio simulations whereas mesoscopic properties shall be derived by embedding the transport behaviour in a continuum description. The project involves active exchange with other groups in the GRK and especially with Martijn Kemerink. A longer research stay in Heidelberg is thus planned.

This project benefits from a solid background in solid state physics, simulation approaches, and statistical mechanics. Familiarity with quantum chemistry calculations and programming in common languages such as Python or C++ are advantageous since participation in the development of employed software tools like MAICoS1 and ESPResSo2 is expected.

1) https://www.maicos-analysis.org/

2) https://espressomd.org/

Responsible E-Mail Latest Revision: 07.06.2023