Optimizing Organic Semiconductor Crystals for Next-Gen Optoelectronics.
Solution-based processing of optoelectronic active layers promises to drive down the manufacturing costs of emerging technologies, such as light-weight, large-area solar panels. While significant effort has focused on the molecular tuning of soluble semiconductors to improve optical and electronic properties, their performance ultimately depends on the extent and manner of crystallization as solvent rapidly evaporates during film deposition. Because organic semiconductors exhibit charge transport anisotropy along different crystallographic directions, controlling the orientation of these crystals is a key parameter in device optimization.
Recently, our group has developed a strategy to use nanoporous scaffolds to orient crystals during the earliest stages of nucleation and growth. Through judicious design of scaffold geometry with respect to crystal growth habits, we can control crystal orientations in up to two dimensions, as well as form unusually-shaped crystals through selective confinement. We are also exploring solvent-free deposition methods of crystallization that induce crystal twisting. Such twisted organic semiconductor crystals exhibit modulated out-of-plane orientations, resulting in regular oscillations in conductivity and fluorescence, as well as unique interactions with circularly polarized light. Â
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Associate Professor
Stephanie Lee joined the Department of Chemistry at New York University as an associate professor in January 2021 and is an affiliated member of the Department of Chemical and Biomolecular Engineering. She received a BS in chemical engineering from MIT in 2007 and a PhD in chemical engineering and materials science from Princeton University in 2012. She was a Provost’s Postdoctoral Fellow in the Molecular Design Institute at NYU from 2012-2014 before joining Stevens Institute of Technology as an assistant professor. Her research group studies the crystal engineering of solution-processable semiconductors for emerging optoelectronic applications, including flexible displays and photovoltaics. Their strategies involve the use of solution rheology to monitor and control semiconducting polymer network formation, scaffold-directed crystallization of small molecules into vertical crystal arrays and nanoconfined crystallization to shift the thermodynamics and stability of metal-halide perovskites for high performance solar cells. Lee is a recipient of the Stevens Early Career Award for Research Excellence and a 2019 NSF CAREER awardee.
