Organic Devices and Systems (ODS)

In the ODS Group physicist, material scientists and engineers are working jointly on the development of novel electronic device concepts for high performance, flexible and possibly even bio-compatible electronics of the future. Based on fundamental investigations on the principles of charge carrier transport in organic semiconductors we develop and optimize novel device concepts such as vertical transistors and integrate them into functional circuits e.g. for wireless communication application. Moreover, we also explore new device paradigms and develop neural networks for artificial intelligence based on organic electrochemical transistors.

A thin-film transistor structure for gated four-point measurements.

Fundamentals of Transport in Organic Semiconductors: In Silicon technology controlled electrical doping and the manipulation of energy levels are well-established and essential for a rational design of electronic devices. In order to adopt these highly techniques to organic semiconductors we pioneered the concept of molecular doping and band gap engineering and investigate basic physics behind these effects. Our current focus lies on the band gap engineering and how this effect can be employed for more energy-efficient optoelectronic devices.

Rubrene crystals: We study the electronic transport properties of highly ordered organic semiconductors that can be integrated into functional devices. Our work includes the growth, doping and processing of thin-film crystals using techniques suited for industrial scale mass production. We are interested in the device physics in novel device concepts based on these ordered organic thin films.

A set of vertical electrodes — vertical organic triodes on flexible PEN substrate.

Vertical Organic Transistors: Traditional, horizontal organic thin-film transistors suffer from the poor charge carrier transport in organic semiconductors. Due to this fact such transistors performance too poor for main demanding electronic applications such as display driving or wireless communication.

stack scheme of organic thin film transistor — integrated vertical organic thin-film transistor device in a configuration for high-frequency measurements.

In the ODS group we pioneered two novel, vertical organic thin-film transistors and triodes which due to their ultra-short vertical architecture are able to operate at frequencies in excess to 100 MHz. These devices clearly outperform other organic transistors and they can even compete with inorganic devices. This allows entirely new applications, for example single-devices with integrated logical functions.

Abbildung einer Probe aus der ODS-Forschung — Flexible and biocompatible pressure sensors.

Biocompatible pressure sensors: Together with ERCD (UKD) we develop biocompatible pressure sensors for a direct measurement of the mid ear pressure. Up to now this is only possible as an indirect measurement or attended with additional surgeries. They can be avoided by our new technique. The usage of an elastic polymer enables a capacitve pessure measurement in a range of +/- 70 mbar. Thereby we incorporate tiny coils in our devices which allow for a wireless communiaction using RFID technology.

Electrochemical Transistors for Neural Networks: Organic electrochemical transistors (OECTs), thanks to their biocompatibility and operation in an electrolytic environment, are envisioned to enable next-generation bioelectronics and ionoelectronics. They have been demonstrated as artificial synapses, biosensors, and drug-releasers. In our group, we go one step further. We grow dendritic networks of OECTs and use them for machine learning. The idea aims at developing implantable and biocompatible computational platforms that can monitor real-time body fluid composition and patterns of biosignals. The random composition of the fibers combined with the machine learning approach of reservoir computing enables artificial intelligence on-chip, a potential breakthrough in healthcare and medicine.