Ligand-Mediated Photothermal Energy Dissipation in Semiconductor Nanocrystals

Research is directed toward a better understanding of the properties of semiconductor nanocrystals. Semiconductor nanocrystals, also known as colloidal quantum dots, are promising components of next-generation renewable energy technologies (including solar cells, high-efficiency lighting, and thermoelectric devices). To improve the performance of these important technologies, more must be learned about how useful forms of energy are degraded into less useful forms (e.g., heat) in these exciting materials. Prof. Tisdale and his team are using advanced optical spectroscopy techniques to study the ways in which thermal energy is generated in quantum dots and developing chemical strategies for preventing these unwanted processes from occurring. In conjunction with these research activities, Prof. Tisdale is integrating new nanotechnology and energy engineering concepts into the MIT Chemical Engineering undergraduate curriculum, and promoting the participation of underrepresented minorities in STEM through a partnership with a Boston public middle school.

Prof. Tisdale and his team investigate the dynamic pathways of vibrational-electronic energy dissipation in quantum dots and in quantum dot arrays, aiming to provide insight into the role of surface ligands in mediating these processes and pointing the way toward more effective quantum dot technologies and more sophisticated models of interfacial heat transport. These efforts include 1) ultralow-frequency vibrational spectroscopy of quantum dots and in quantum dot arrays, including the use of time-domain and frequency-domain techniques for observing surface vibrational modes and coherent lattice dynamics in ordered quantum dot arrays; 2) frequency-resolved visualization of thermal transport in quantum dot arrays, including the development of a novel time-resolved optical microscopy technique; and 3) ultrafast dynamics of vibrational relaxation in QDs, with a particular emphasis on the interaction between hot electrons and surface ligands.