Advanced nanoscale characterization of organic photovoltaic materials

In order to explore the full potential of organic photovoltaic (OPV), there is a number of
scientific challenges regarding material properties and their integration in device
architectures to be overcome. A prepared sample of an OPV is shown in figure 1. In a) the
layer structure can be observed, which was recorded using a transmission electron
microscope (TEM). A photo-active layer (AL) and a zinc-oxide layer (ZnO) have been
deposited on a PEN foil and fixed by a gold layer (Au) and an embedding medium (EBM). In
b) the thickness of the layers could be determined on the basis of their intensities in the
nanometer range.
In future, unwanted reactions and degradation effects in the active material and at the
interfaces of an OPV cell will be identified by means of analytical Cs-corrected scanning
transmission electron microscopy (STEM). By combining state-of-the art high sensitivity
spectroscopic techniques like electron energy loss spectrometry (EELS) and energy
dispersive X-ray spectrometry (EDX) with novel imaging and diffraction techniques, chemical
and structural changes will be identified to contribute to the development of mitigation
strategies. Due to the sensitivity of these materials, innovative preparation and analysis
methodologies, including machine learning and smart acquisition strategies have to be
applied and adapted.