Collaborative Research: Electric Field- and Light-Modulated Thermal Transport in Superatomic Crystals

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The ability for a material to transport heat is governed by its thermal conductivity. High thermal conductivity materials are thermal conductors, while low thermal conductivity materials are thermal insulators. The objective of this project is to discover materials whose thermal conductivity can be quickly changed. Such thermal conductivity switches will be useful in reducing the temperature of electronic devices that intermittently overheat and in converting heat into electricity. The proposed approach is based on controlling the rotations of molecules inside a new class of material called superatomic crystals. When the molecules rotate, the thermal conductivity is low. The application of an electric field or light will cause the molecules to stop rotating and increase thermal conductivity. The supported graduate students will be recruited from diverse pools and will gain cross-cutting experimental and modeling experience in chemistry, thermal transport, and materials science. The team will develop educational modules to expose middle school, high school, and undergraduate students to the links between a material’s atomic structure and its properties.Superatomic crystals are assembled from precise molecular building blocks called superatoms. Their scalable synthesis and multi-functional properties make them attractive for energy conversion applications. Orientational disorder (i.e., rotation) of C60 superatoms in some superatomic crystals at elevated temperatures decreases their thermal conductivity. The overarching hypothesis of this project is that C60 orientational disorder can be actively manipulated using electric fields and light. Through synthesis and crystallography at Columbia and thermal transport measurements and atomistic modeling at Carnegie Mellon, this hypothesis will be tested on the novel superatomic crystal [Co6Te8][C60]3. Polar intercalants and photoactive ligands, triggered by electric fields and light, will become monkey wrenches that lock the C60 gears of the superatomic crystals to switch thermal conductivity on demand. Such thermal switches can be used to create transient heat fluxes from steady-state sources to improve the performance of pyroelectric and thermoelectric devices. Thermal switches will also enable active control of heat pathways and new approaches for managing heat in electronics. Three interdisciplinary tutorials will introduce chemistry students to thermal transport and engineering students to chemical bonding and superstructures. Outreach activities in underserved communities in Pittsburgh and New York will expose middle and high school students to the intersection of chemistry and engineering. The graduate students supported by the project will be recruited from diverse pools and will gain interdisciplinary experience in chemistry, X-ray crystallography, optics, and computational materials science.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.