University of California, Riverside

Department of Electrical and Computer Engineering

Nanostructured Thermoelectric Materials and Devices

Nanostructured Thermoelectric Materials and Devices

Nanostructured Thermoelectric Materials and Devices

June 19, 2013 - 2:40 pm
Winston Chung Hall, 138


Thermoelectric semiconductor materials and devices can enable a wide array of applications in solid state cooling of electronics and compact air-conditioning systems as well as energy harvesting in many scenarios including solar-thermal, automotive exhaust heat, industrial waste heat, etc. One of the two major limitations in the widespread use of thermoelectric technology has been the materials figure of merit (ZT) and the other being the ability to translate the enhanced materials’ ZT to a device performance, overcoming various device electrical and thermal losses. These limitations have significantly curtailed the widespread use of semiconductor-based thermoelectric devices since their original development in 1950’s, at about the same time semiconductor-based transistors rose to prominence, even though they offer several advantages like reliability, noise-free operation, and a green technology. Nanoscale materials based on superlattices, nano-dots, nano-wires and nano-bulk materials with second phases or nano-inclusions have become the dominant approaches to enhancing the ZT in thermoelectric materials since 2001 (Nature 413, 597 (2001)) and they have been further validated recently (Nature 451, 163 (2008), Nature 451, 168 (2008) and Science 320, 634 (2008)). Almost all of the recent successful efforts in ZT improvement have been a result of the significant reduction in lattice thermal conductivity through phonon scattering in nanostructures, without affecting the electrical transport of electrons or holes, by the so-called phonon-blocking electron-transmitting structures. Studies on the phonon-transport using femto-second optical and acoustic phonon property measurements have provided further understanding of the physics behind thermal conductivity reduction in superlattices. Careful band offset measurements have been carried out to understand and model carrier transport across interfaces in several superlattice systems. Recent work in ultra-low-dimensional systems to take advantage of the exciting physics of topological insulators will be discussed. Device developments using advanced nanoscale superlattice thermoelectric materials, like hot-spot cooling of high performance electronics (Nature Nanotechnology 4, 235 (2009)), as well as power generation with nano-bulk thermoelectric devices for solar-thermal systems and waste heat harvesting would be presented. Biomedical applications of thin-film thermoelectric technologies would be presented as well.


Dr. Venkatasubramanian (Ph.D. Rensselaer, New York, 1988; B.S. Indian Institute of Technology, Madras, India, 1983; Electrical Engineering) is currently dedicated to the innovation and advancement of several solid state energy efficient materials and device technologies as well as transitioning them to the industry. Until April 2013, Dr. Venkatasubramanian was the Senior Research Director of the Center for Solid State Energetics at RTI International, where he directed innovative basic and applied research in thermoelectrics, photovoltaics, and optoelectronic materials and devices for solid state energy conversion applications. Dr. Venkatasubramanian is the Founder and was also the Chief Technology Officer of Nextreme Thermal Solutions, between 2004-2006, which is commercializing thin-film thermoelectric technology developed under his leadership with DARPA funding; Nextreme was recently acquired by Laird Technologies in Feb. 2013. Dr. Venkatasubramanian has over 115 peer-reviewed journal and conference publications, 15 issued patents, over 100 presentations in the area of thermoelectric materials and devices, photovoltaics, optoelectronics, and 5 book chapters and edited proceedings. Dr. Venkatasubramanian initiated and developed a research program focused on demonstrating the fundamental advantages of atomically engineered superlattices and other nanoscale materials at RTI; this research resulted in the first major breakthrough in the field of thermoelectrics in 40 years (Nature 2001, Nature Nanotechnology 2009), that led to hundreds of laboratories around the world working on other nanoscale thermoelectric materials. Dr. Venkatasubramanian has received the R&D 100 Awards in 2002 and 2010 for thermoelectric innovations, the Margaret Knox Excellence Award for research at RTI in 2002 and Rensselaer’s Allen B. Dumont Prize for research achievements. Dr. Venkatasubramanian was elected Fellow of the IEEE (2011) for contributions to nanoscale thermoelectrics for thermal management of electronics and energy harvesting and a Fellow of AAAS (2012) for seminal contributions to nansocale materials and devices for advanced thermoelectric devices. Dr. Venkatasubramanian has also contributed to advances in multi-junction GaAs-based photovoltaics, received a best paper award at the IEEE First World Conference on PV (1994), and his photovoltaics work was recognized as key achievements by Department of Energy in 1995, 1996, 1997. Dr. Venkatasubramanian serves as an Editor of the IEEE Transactions on Electron Devices, has organized several symposia and has edited proceedings in thermoelectrics, energy harvesting and nanoscale thermal transport for the American Physical Society, Materials Research Society, IEEE and other professional societies.



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Electrical and Computer Engineering
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