There remain significant challenges in achieving stable, high performance organic semiconductor devices from scalable manufacturing methods. We address this using synchrotron-based X-ray scattering and a variety of optical methods to observe the structure of films in-situ as they dry. I will review our studies of systems including organic photovoltaics (OPVs) which can achieve nearly 10 % power conversion efficiency (PCE), and organic thin film transistors (OTFTs) that can achieve high (>1 cm2/Vs) hole or electron mobility. I will emphasize commonalities and differences among systems, and attempt to classify the processing behavior of systems based on traits such as diffraction strength (~crystallinity). There is a surprising diversity of solidification mechanisms among organic semiconductor systems. Some are dominated by the nanoscale crystallization of the components, whereas others appear to be dominated by liquid-liquid phase separation. I will also touch on the role of additive ink formulations. Examples of good performance can be found for systems that have many different types of final morphologies that are produced by different solidification mechanisms.
The diversity of morphologies that can produce high performance in organic semiconductors suggests that there is no single morphological trait that can be depended on to predict performance. New measurements may be needed that can probe the nanoscale distribution of molecular orientation. I will describe our further development of resonant soft X-ray scattering, which combines principles of spectroscopy, small-angle scattering, real-space imaging, and molecular simulation to produce a molecular scale structure measurement that probes these previously inaccessible aspects of organic semiconductor morphology.