Research areas:
Projects
Self-assembly organization of organic molecules in bulk and thin film
Large-area flexible, organic electronics, including personal devices - medical sensors, but also high-tech electronic systems - logic gates, suffer from non-uniform electrical operation between single devices (field-effect transistors) related to the heterogeneity of the active layer caused by local changes in molecular organization, variability in thin layer crystallinity and repeatability of the deposition process. In order to meet these requirements, the aim of this project is to understand and control the nucleation and crystallization process during solution deposition of organic semiconductors (OSCs) on large area. The understanding of the heterogeneous, induced nucleation and crystallization process as a function of semiconductor chemical structure, self-assembly properties and processing parameters is a key parameter to obtain stable and repeatable charge carrier transport on large area. To recognize the relation between crystallinity, surface morphology and charge carrier transport, various (low and polimeric) semiconductors are under characterization.
Microstructure, long-range organization of organic, inorganic and biomolecules
The supramolecular organization in bulk and in thin films can be investigated by two-dimensional wide-angle X-ray scattering (2D-WAXS) and grazing-incidence wide-angle X-ray scattering (GIWAXS), respectively. The bulk measurement are performed on the 1 dimensional fibre prepared by mechanical extrusion in respect to the thin films which can be deposited on rigid and flexible substrate by thermal evaporation or solution processing. Both X-ray methods give valuable information about molecular organization of the low and high molecular weight organic (semiconductors, biomolecules) and inorganic (perovskite) materials. Variation in the chemical structure, substituent position and role of deposition procedure can be easily determined by 2D-WAXS and GIWAXS experiments.
Both techniques are used to characterize organic and inorganic materials which can be applied in light emitting diodes, photovoltaics (Nature Communications, 2019, 10:2867, Adv. Energy Mater., 2017, 7, 1601733), photodetectors (Adv. Optical Mater. 2022, 2102397) and biological sensors (Adv. Electron. Mater. 2019, 5, 1800804).
Definition of self-assembly properties on thin film morphology and charge transport in organic semiconductors
In the frame of this task, understanding of the crystallization process of organic semiconductors as a function of chemical structure, solvent and processing parameters is investigated following already published reports: Adv. Funct. Mater. 2022, 32, 2107976, Nature Materials, 2021, 20, 68. Control of the crystallization process of different semiconductors deposited by various thermal and solution techniques allows to reduce of thin-film defects in terms of domain size, shape anisotropy and grain boundary density, which finally influence the charge carrier transport (Adv. Electron. Mater. 2021, 7, 2100397). Combination of the experimental work with theoretical prediction will show improved device performance and demonstrate upscaling feasibility. The mentioned research areas of crystalline semiconductors can be extended not only to field-effect transistors (currently main application area in Marszalek group) but also to light emitting diodes and solar cells or any other research field consisting crystalline semiconductors.
Organic field-effect transistors
Nowadays, almost all electronics systems are based on inorganic materials. Fully developed silicon technology allows to produce high performance, low power and ultra-miniature devices. Charge carrier mobilities up to 103 cm²/Vs, operation voltage of around 1 V and channel length of ca 45 nm are the main advantages of silicon-based technologies. However, the high costs of silicon-based devices which are attributed to the sophisticated silicon wafer processing, handling equipment, clean-room environmental make them too expensive for certain industrial applications. Small displays, radio-frequency identification (RFID) tags, sensors and disposal electronics require transistors of low-cost materials and processing techniques. In such situation, organic electronics found the way from basic academic research to industrial applications over recent years in a quickly growing market. However, a complete technology requires upgrading of fabrication procedures of all elements of electronic devices and circuits, which not only comprise active layers, but also electrodes, dielectrics, insulators, substrates and protecting/encapsulating coatings.
Targeted applications include:
- Identification and characterization of the bottlenecks in organic field-effect transistors
- Role of the atmosphere and mechanical bending on the charge carrier transport in thin semiconductor films
Perovskite field-effect transistors
Dr. Marszalek is also highly interested in perovskite transistor technologies. Preliminary obtained results confirm that his knowledge gained for organic semiconductors can be successfully transferred into inorganic technology and can significantly improve the transistors performance and their further application. In order to improve transistors performance: charge carrier transport and air stability, Marszalek group has started cooperation with Prof. Mischa Bonn (Terahertz spectroscopy) and Dr. Denis Andrienko (Theory and simulation in Organic Electronic) from Max Planck Institute for Polymer Research. The preliminary obtained data (Materials Horizons, 2022) confirms that scientific input from Marszalek group could be valuable for perovskite community. Next high quality scientific papers are under preparation.
Targeted applications include:
- Control of microstructure and surface morphology in thin perovskite film
- Air and bias stress stable perovskite transistors
Flexible electronics with wearable/implantable device
The technological significance of flexible organic devices could rely on sensors for human body or wearable electronic component. For example, sensors placed on the skin, so-called electronic skin, must contain circuits that do not lose their electronic properties while being stretched on extending and contracting muscles. These sensors can collect body parameters to continuously monitor the state of the patient and transmit this information to the medical doctor. In this uninterrupted monitoring, the medical doctor can notice on the change of body parameters and can react even before a critical emergency happens. The same is valid for sensors placed, for example, on the patient’s heart to monitor its functions or as another example for heart catheters. In such case, one could imagine that not only information is collected to send to the doctor, but in the case of emergency, the stretchable device can also act as pacemaker and implantable defibrillator which is controlled by sending corresponding stimuli by the doctor located far away from the patient. In this way, it would be possible to stop the arrhythmia and prevent sudden cardiac death. For these reasons, the health care sector is highly attractive for bendable and stretchable electronics. Due to the advanced functionality of these devices (stretchability and electronic operation), higher production costs related to the synthesis and processing of the organic semiconductors could be most probably justified and well accepted.
We expect to achieve the following milestones in the frame of Functional Materials Technology and Optical Nano-characterization – research area:
- Fabrication of flexible and stretchable organic field-effect transistors for wearable electronics for biomedical applications;
- Electronic skin based on flexible and stretchable organic transistors.