Molecular-Level Insight to Charge Carrier-trapping Defects on Semiconductor Nanocrystal Surfaces

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professors Jillian Dempsey and Yosuke Kanai of the University of North Carolina at Chapel Hill are studying how defects on the surface of nanoscale materials impact energy flows through these materials. They are also examining how different types of defects on the surface can be repaired through selective chemical reactions. Their work will combine experimental work with advanced theory that probes these materials on the atomic level. Through this work, they will learn how to repair defect-rich materials to access high performing materials that can be used in sensing applications, display technologies, solid state lighting, and photon energy harvesting. Through this project, Professors Dempsey and Kanai will help prepare students for the STEM workforce, providing them with comprehensive training in materials science, chemistry, and theory. They will also develop and deploy hands on activities at science festivals, introducing K–12 students and their families to the applications of nanomaterials. With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professors Jillian Dempsey and Yosuke Kanai of the University of North Carolina at Chapel Hill are using the tools of molecular chemistry and atomistic theory to probe the structural identity and energetics of surface-based defects which trap charge carriers on semiconductor nanocrystals. They will apply selective ligand addition and exchange reactions to passivate or expose specific defect sites. Subsequently, they will combine spectroscopy with simulation to learn how these surface-based states influence charge carrier dynamics. This work will ultimately provide molecular-level details and energetics of charge carrier trap states on semiconductor nanocrystal surfaces. Explicit principles by which these states can be chemically and electronically passivated will be obtained, providing an enhanced understanding of how to rationally mitigate surface-based defects. This knowledge will enable enhanced performance of nanocrystal-based optical devices with applications in sensing, display technologies, solid state lighting, and solar energy harvesting. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.