Control of Light-Induced Electronic Behavior at Interfaces of Hybrid Nanomaterials

Padgaonkar, Suyog

doi:https://doi.org/10.21985/n2-p4kt-nz04

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Control of Light-Induced Electronic Behavior at Interfaces of Hybrid Nanomaterials

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This dissertation explores ways to utilize physical parameters at the nanoscale interface to control the properties of mixed-dimensional heterojunctions (MDHJs). MDHJs combine the desirable properties of different classes of low-dimensional nanomaterials (materials that are quantum confined in at least one dimension). While MDHJs have achieved superlative performance for a variety of optoelectronic applications through this approach, they present even more opportunities to achieve emergent and exotic behavior. Because these low-dimensional materials have large surface-to-volume ratios, they are sensitive to small changes in their physical environment. This sensitivity can be leveraged to tune the properties of MDHJs by altering physical parameters at the mixed-dimensional interface. This dissertation focuses primarily on a few examples that develop a means to control over the rates and yields of charge and energy transfer between low-dimensional materials because this understanding is key to their future use in applications. The molecular orientation of organic molecules on the surface of a two-dimensional material can control the lifetime of charge separation at the mixed-dimensional interface. Different wavelengths of light can control the photoluminescence of quantum dots by leveraging the change in the rate of charge transfer to bound photoswitchable ligands. The light harvesting ability of chemically-reactive black phosphorus (BP) is enhanced by utilizing energy transfer from a close-packed film of quantum dots through a protective encapsulation layer to the BP. Beyond developing control over rates of charge carriers across the mixed-dimensional interface, physical parameters in MDHJs can be altered to achieve even more exotic phenomena, such as exciton delocalization, spin selectivity, and quantum emission, in MDHJs. Finally, beyond the fundamental understanding of the properties of MDHJs, this dissertation looks beyond the lab and describes the development of a science outreach program to explain current research to senior citizens and other voting-age populations, which is critical because the broad understanding of basic scientific research is key to a more informed society.

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