253575 Tuning the Molecular Packing of Organic Semiconductors for High Performance Using Metastable Crystallization

Sunday, October 28, 2012
Hall B (Convention Center )
Gaurav Giri and Zhenan Bao, Chemical Engineering, Stanford University, Stanford, CA

Solution deposition of organic semiconductors (OSC) is a leading contender for producing large-area, inexpensive, and flexible organic electronics. Our work involves using a new solution processing technique called solution shearing in order to cause OSC crystal lattice strain and thus 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 the stability of the novel molecular packing structure and also measure the relationship between the morphological features and its impact on charge carrier transport. We also develop an in-situ technique that uses X-ray diffraction to study how the strained crystals grow as a function of solution shearing parameters. This in-situ technique utilizes high speed optical and X-ray diffraction imaging (~100 fps) in order to study OSC crystal growth. My proposed research will expand on the concept of metastable crystallization of OSC and other organic molecules in order to reliably generate new polymorphs and strained crystals. Through the use of confined and controlled solvent evaporation, novel solute packing motifs can be achieved. X-ray diffraction and differential scanning calorimetry (DSC), among other techniques, can be used to screen for these crystal polymorphs.

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