Scientific Concept

Conjugated organic materials form the basis of emerging new core technologies like optical displays, field effect transistors and photovoltaic cells. Liquid crystal displays (LCDs) are currently the standard material for flat panel display applications, while organic light emitting diodes (OLEDs) show a steadily increasing significance for future displays and organic thin film transistors (OTFTs) are highly desirable for flexible displays and sensors. Closely related to OLEDs and OTFTs is the field of organic photovoltaics (OPVs), also referred to as solar cells which offers the best technology for a sustainable energy supply.

Further progress in this area is mostly limited by two reasons; first, the charge carrier mobility in organic semiconducting materials is considerably lower than in inorganic semiconductors. This is a consequence not only of the localization of the electronic orbitals in molecules, but also a result of the - mostly - amorphous local packing and the presence of many grain boundaries. Liquid crystalline order can help to increase the local order without the creation of too many grain boundaries. Recent studies have shown that through proper control of order, charge carrier mobilities as high as 1.1 cm²/Vs can be achieved.

A second major issue concerns the control of the interface and the phase separated superstructure between p- and n-type conducting materials in OPVs (or donor and acceptor materials) in order to optimise charge separation and the effective migration of charges to the connecting electrodes. Redox and energy transfer processes at interfaces are also very important for organic LEDs, where especially the interface between organic and inorganic materials has to be taken into account. Here, charge injection, quenching of excited states and the chemical stability are determining factors. Thus it is essential to investigate the interface in more detail and to improve concepts to control the interface characteristics and phase separated superstructure. Towards this end, we want to combine in particular, methods for morphology characterisation with that of electrical characterisation. A combination of AFM and Kelvin probe measurements can simultaneously provide information on both of these characteristics.

Therefore, to make any significant progress in this area it is necessary to include self-organized structures for an increase of the local order and a control of the superstructure and to combine in one team, the expertise to (i) synthesize new materials, (ii) developments of new concepts for forming functional structures by self-organization, (iii) better understand the basic processes at interfaces and (iv) combine engineering skills to turn knowledge into applicable science. Research in such broad range of topics cannot be performed at one place and is only possible at an international level.

For a successful work within such an interdisciplinary framework the topic will be divided into four work-packages. Some applicants for the IRTG may contribute to several work-packages with different intensity. Side activities are marked in italics.

The titles of the work-packages are: