Functional Materials

Course with Participations of Group Members

Offers for Theses in the Group

High efficiency next generation organic solar cells

Next generation organic solar cells are solar cells beyond the silicon type photovoltaic devices. Organic solar cells have reached efficiencies in the champion solar cells well above 18%. Key element of such solar cells is the highly designed active layer, which transfers light into separated charge carriers. Aim of this experimental project is the preparation and full characterization of an active layer for high performance organic photovoltaic devices to further understand the fundamental correlation between morphology and solar cell performance. In this work a novel efficiency record-setting system will be investigated regarding the influence of an additional third component, in our case, either solvent additive or polymer. The project will involve a literature review, sample preparation, photovoltaic device fabrication and photoluminescent measurements. The focus is the usage of advanced scattering techniques for the determination of structural length scales of the active layer in the solar cell.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Implementation of region-of-interest mode in diffraction computed tomography

Implementation of region-of-interest mode
in diffraction computed tomography

Since its development, X-ray tomography became a non-alternative tool for fast and non-destructive characterisation of different objects providing an in-depth resolved information from the interior of materials, devices and living organisms. Besides the overall popularity and the widley use of the method it suffers heavily from contrast limitation issues, which are directly related to the underlying properties of X-ray attenuation. One of the approaches to enhance the sensitivity of the method (at least in the field of solid-state applications) is the utilization of a diffraction-based input signal instead/together with the absorption-based signal information. X-ray diffraction radiography – a scanning technique taking XRD pattern at each scanning position\pixel (and tomography, as its logical continuation) is a relatively new method for sample characterisation, which requires requiring a large amount of diffraction data as input. However, it is capable to provide unique information about the organisation and composition of the studied objects. The size of diffraction data in a XRD-CT dataset is one of the limiting factors for the resolution of the measurement, i.e. for larger samples. A possible solution for this would be a limitation to certain region-of-interest within the objects volume. Thus, the aim of the proposed thesis is the validation of available approaches for reconstruction of XRD-CT data in the region-of-interest mode and its application for non-destructive studies of cylindrical Li-ion batteries.

Common supervision is foreseen with Dr. Anatoliy Senyshyn, diffraction group leader at MLZ.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Winfried Petry

Lightweight Organic Solar Cells as Alternative to Nuclear Batteries for Deep Space Power Generation

The exploration of the outer solar system so far relied heavily on the use of scarce, highly radioactive plutonium stockpiles for power generation, as traditional solar cells have a too low power-to-mass ratio in low light environments to be suitable for those missions. Latest advances in organic solar cells now open up the possibility of utilising them on lightweight foils as photovoltaic solar sails for efficient power generation in low solar irradiation conditions. We have just recently successfully demonstrated the first power generation of organic solar cells on a suborbital space-mission, featuring our in-house developed "Organic and Hybrid Solar Cells In Space" (OHSCIS) experiment. While this demonstration still employed a more traditional, non weight-optimised solar cell design for more typical earth-bound applications, your task will now be to further optimise the design and material selection to reduce the mass of our organic solar cells for our next upcoming space-mission. The solar cells you build will then take part in this mission and be launched into space.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Lithium-ion batteries with modified electrolyte for next generation batteries

Lithium-ion batteries are an indispensable energy supply in modern society. The ideal anode consists of lithium metal due to its high specific energy and low electrochemical potential. However, lithium-ion batteries with liquid electrolyte are prone to form lithium dendrites, which can lead to failure or even explosion of the battery. Therefore, polymer electrolytes are an attractive alternative to bypass these obstacles. However, polymer electrolytes suffer from high contact resistances and low ionic conductivities, which requires an elevated operating temperature. In this project, a hybrid electrolyte based on liquid electrolyte modified with polymer will be prepared. Then, CR2032 coin cell batteries will be fabricated and tested with standard cycling procedures. Besides electrochemical characterization techniques, complementary measurement like real space imaging techniques (scanning electron microscopy, SEM) and reciprocal space techniques (small angle x-ray scattering, SAXS) can be performed. Overall, this master thesis project involves literature review, sample preparation and data analysis.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Low-temperature fabrication of titania films for hybrid solar cells on flexible substrates

Low-temperature (<150°C) route towards titania films offer promise for simple manufacturing, compatibility with flexible substrates, and titania-based solar cells. Herein, we use a specific titania precursor, ethylene glycol-modified titanate, to fabricate titania films as an electron-transporting layer. This experimental bachelor thesis aims at understanding the working principle of hybrid solar cells and the corresponding fabrication process. Different film characterization will be used such as SEM, GISAXS, XRD, UV-Vis, XPS, etc. The project will involve a literature review, sample preparation process, data analysis and result evaluation.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Optically controlled automatic sample positioning system for scattering/diffraction applications: conceptualisation and development

Accurate, controllable and reproducible sample positioning is necessary for a variety of experimental techniques utilizing laser, X-rays, electron beams and/or neutrons. For the diffractometers at the FRM II neutron source a fully automatic sample positioning system is required, which, in conjunction with a robotic sample changer, will be the base for an automatized experimental pipeline. The mechanical core of the system will be a stepper motor driven goniometer head from Huber, possessing five degrees of freedom. The movement, detection and control will proceed by a silhouette detection system based on telecentric optics. The tasks of the proposed thesis will include: conceptualisation and building up of telecentric optical control system, the optimisation of data readout, the development of fully automatic alignment algorithm, the integration of the components into NICOS system (Python driven) and the validation of the system in real measurements with neutron scattering and/or synchrotron radiation. Common supervision is foreseen with Dr. Anatoliy Senyshyn, diffraction group leader at MLZ.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Winfried Petry

Printed perovskite solar cells

Organic-inorganic lead halide perovskite solar cells have recently achieved 25.5% efficiency owing to their tunable bandgap, high carrier mobility and long diffusion length. Nevertheless, most of the solar cells were fabricated based on the spin-coating method, which suffers from waste of material and missing scalability. In this regard, the printing technique, a simple and scalable method, is advantageous to realize a future commercial application of perovskite solar cells. In this project, we aim to fabricate perovskite solar cells by printing and have an overall understanding of the growth mechanism of the perovskite film during printing. We use imaging techniques (e.g. electron microscopy) and methods for structure and morphology determination, e.g. X-ray scattering.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Printed polymer-based thin film batteries

Materials for high energy density, solid-state batteries have been tremendously explored in the last decade. In particular, lithium-ion technology has attracted major interest. Among the many different types of batteries, the so-called polymer-based thin film batteries are very attractive as they can be incorporated into thin film devices. An inherent important part of such thin film lithium ion batteries is the membrane and solid-state polymer electrolyte membranes have attracted high attention in this respect. Lithium ions’ incorporation into solid-state polymer electrolyte membranes had shown a significant effect on both, the structure and properties, of the membranes in either the bulk or film format. The morphological reorganization and the thermodynamic properties of the solid-state polymer electrolyte membrane upon adding lithium salts and small molecules are the subjects of the experimental investigation. The polymer membranes will be prepared with printing. The structure and crystallinity of the lithium-doped membranes at different temperatures will be investigated with small/wide-angle X-ray scattering (SAXS/WAXS). The effects of morphology on the ionic conductivity of these ion-conducting membranes will be investigated using impedance spectroscopy. Aim of the present study is to increase conductivity with the help of small molecule additives, which can further improve the membrane morphology beyond the possibilities of the standard approach. Such high conductivity will be very beneficial for further downsizing of polymer-based thin film batteries.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Quantification of local aging behaviour in lithium-ion batteries

Quantification of local aging behaviour in lithium-ion batteries

Lithium-ion batteries are nowadays the primary energy storage system in electric driven vehicles and portable electronic devices. Thus, a continuous improvement of lithium-ion batteries is mandatory to meet the increasing energy demand on the market. One of the main branches of today’s research deals with the minimization of aging effects occurring in lithium-ion batteries and taking place during cell operation. In the proposed project, the state-of-health at different areas of a working electrode in real lithium-ion batteries will be determined in order to create a 2D “map” of the state of fatigue distribution. Thus, commercially available lithium-ion batteries will be electrochemically cycled and disassembled in order to harvest the electrode materials. Fragments of the extracted electrodes collected at various positions over the electrode sheets will be analysed as coin cells with various characterization techniques, such as impedance spectroscopy, cycling voltammetry and galvanostatic intermittent titration technique. The project will be completed with X-ray diffraction measurements of the collected electrodes.

Common supervision is foreseen with Dr. Anatoliy Senyshyn, diffraction group leader at MLZ.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Winfried Petry

Smart nano-sensors made of stimuli-responsive polymers in solution and in thin films

Whereas macroscopic sensors made of stimuli-responsive hydrogels are well established, in the nanoworld such sensors still face many challenges. Potential fields of application of such sensors extend from engineering to bioengineering and medicine, e.g. as nanosensors for the control of concentration of glucose for diabetes patients or as switchable surface in the frame of tissue engineering. In this experimental project smart hydrogels, made of stimuli-responsive hydrogels will be investigated. Hydrogel films with thicknesses of a few tens to some hundreds of nanometers and spontaneously deswell or swell due to external stimuli, like temperature or the concentrations of ions. The changes in thickness and in molecular interactions in swelling or collapsing hydrogels will be probed during the switching process by different lab-based techniques. A comprehensive understanding of the switching process can be achieved by complementary neutron scattering experiments at large scale facilities. The project will involve a literature review, preparation of hydrogels, as well as experimental investigations and interpretations of the repeated switching of the stimuli-responsive hydrogels.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Synthesis and self-assembly of gold nanoparticles for optoelectronic devices

Gold nanoparticles (Au NPs) show peculiar optical and electrical properties compared with the macroscopic metal owing to the characteristic of a nanoscale. Recently many advantages were made in optoelectronic devices applications with broadening band and energy transfer. In this project, your work will focus on the Au NPs structure regulation, since the size, density, and morphology of the Au NPs will influence the crystallinity of the photoactive film and charge transportation of the device. Specifically, you can work on one of the following topics: a) Synthesis and investigate optical properties of different morphology of gold nanoparticles b) Self-assembly of monolayer Au NPs array for optoelectronic devices.

suitable as

• Master’s Thesis Applied and Engineering Physics

Supervisor: Peter Müller-Buschbaum

Current and Finished Theses in the Group