Carnegie Mellon University
March 20, 2013

Press Release: Carnegie Mellon Professors Use Nanocrystal Arrays To Explore Novel Heat Flow In Hybrid Materials

Researchers Break Barriers With New Thermal Science Research

Contact: Chriss Swaney / 412-268-5776 /

PITTSBURGH-Carnegie Mellon University's Jonathan A. Malen and Alan J. H. McGaughey are leading a multidisciplinary team of researchers exploring how heat is transported in organic-inorganic hybrid materials.

The nanocrystal arrays they are studying are cost-effective potential replacements for single-crystal semiconductors in solar cells, solid-state lighting and thermoelectric energy generators. Thermal management challenges exist in all these technologies. For example, excess heat generation in solid state lighting leads to higher operating temperature and reduced performance, lifetime and reliability.

Previous works on nanocrystal arrays, however, did not consider any thermally related behavior or properties. The Carnegie Mellon researchers, in collaboration with colleagues at the University of Chicago, made the first-ever measurements of thermal conductivity in this new class of material.

Nanocrystal arrays are built from nanometer-sized semiconductor spheres linked together by small organic molecules in a periodic arrangement. Endless material combinations, paired with size tunability and scalable manufacturing, make nanocrystal arrays an exciting next-generation material for energy-related applications.

In their Nature Materials letter titled "Surface chemistry mediates thermal transport in three-dimensional nanocrystal arrays," CMU Ph.D. student Wee-Liat Ong and Mechanical Engineering professors Malen and McGaughey teamed up with chemistry Ph.D. student Sara Rupich and Associate Professor Dmitri V. Talapin, both of the University of Chicago, to demonstrate that nanocrystal size and composition can tune the thermal conductivity of nanocrystal arrays.

Such trends result from the physics occurring as energy carrying vibrations traverse organic-inorganic interfaces, as highlighted by a News and Views perspective in Nature Materials titled "Breaking through barriers."

"Our work transcends several fundamental disciplines and has a direct impact on heat dissipation in organic-inorganic hybrid materials. Novel hybrid materials could be the next big thing in energy, where conventional semiconductors cannot be scalably produced and organic polymers cannot perform," Malen said.
The research team reports that the relatively low thermal conductivities of the nanocrystal arrays pose immediate challenges to heat dissipation in electronics and photonics. These properties, however, may actually be beneficial to thermoelectric energy conversion devices that are poised to improve energy efficiency by scavenging waste heat from power plants, automobiles, and even hand-held electronics. This landmark study provides a starting point for the conversation.