(6ao) Crystal Polymorphism and Texture Control during Solution Growth for Organic Electronics and Pharmaceutical Flow Chemistry

Giri, G., Massachusetts Institute of Technology
Jensen, K. F., Massachusetts Institute of Technology
Bao, Z., Stanford University

Solution deposition of organic semiconductors (OSC) is a leading contender for producing large-area, inexpensive, and flexible organic electronics. Using a new solution processing technique called solution shearing, we modify the molecular packing of a wide range of OSCs through processing alone. We quantitatively measure the molecular ordering resulting from different deposition conditions and show effective tuning of molecular packing that yields higher charge carrier performance without changing the underlying chemical structure. We investigate how solution flow and evaporation affects the morphological features and their impact on charge carrier transport. We also develop a novel high speed in-situ technique that uses X-ray diffraction to study how the polymorphs grow as a function of solution shearing parameters. This in-situ technique shows that the confined growth of OSC in a thin film promotes formation of a metastable crystal polymorph. We pattern high performance organic electronics through the use of surface selective patterning and nucleation control. The concept of nucleation control and crystal growth is also utilized to perform and extend microfluidic flow chemistry for pharmaceutically relevant reactions. Inorganic and organic solid formation can be processed without clogging the reactor by understanding the characteristics of crystals in flow. My proposed research will expand on the concept of metastable crystallization of OSCs and other organic molecules in order to reliably generate new polymorphs while controlling crystal morphology.