"Microstructure Foundations of High Performance in Organic Semiconductors"

Dean M. DeLongchamp
National Institute of Standards and Technology
Gaithersburg, MD

Abstract:

Organic semiconductors enable new and low-cost methods to mass-produce flexible sheets of light-emitting diodes, transistors, solar cells, and sensors. A key enabling feature of organic semiconductors is their solubility in common solvents, which permits deposition and patterning by simple printing, but requires that the semiconductor microstructure develop dynamically as an applied solution dries. The semiconductor films can have microstructure variations over length scales ranging from the intermolecular to the macroscopic, and these variations can make or break the performance of organic electronic devices.

We develop benchtop and synchrotron-based measurement methods to characterize the interfacial structure of organic semiconductors with respect to processing methods, processing variables, and primary chemical structure. A combination of polarized absorption spectroscopies (infrared, visible, and synchrotron X ray), scanning probe microscopy, and synchrotron X-ray diffraction are applied to reveal details of microstructure at organic thin film transistor (OTFT) interfaces. These measurements establish clear correlations between primary chemical structure, processing, film microstructure, and OTFT performance. These fundamental relationships lead to practical guidelines for synthesis and processing. The many potential opportunities for performance enhancement indicate a promising future ahead for organic electronics.