Material Detail

Thermoelectric effects are based on the difference between the average energy of the conduction electrons (or holes) and the Fermi energy. A thermoelectric material can be configured into a device for solid-state refrigeration or electrical power generation. Although these devices are presently restricted to niche applications - including beverage coolers, temperature control of communications lasers, and radioisotope thermoelectric generators for deep space probes –there is great potential for widespread application if the materials can be improved. In particular, an increase in the materials’ dimensionless figure-of-merit, ZT, from today’s values of ~1 to values above 4 would enable replacement of compressor based refrigeration with a solid-state alternative. Applications such as conversion of waste heat from vehicle exhaust to electric power would also become feasible. The key to designinghigh ZT materials is to manipulate phonons and electrons at the nanoscale. Confining electrons and holes can enhance the numerator of ZT, known as the power factor. Introducing defects that scatter phonons but not electrons can decrease the thermal conductivity (the denominator of ZT) without appreciably affecting the power factor. In this tutorial, I will review recent strategies for designing high-ZT nanostructured materials, including superlattices, embedded quantum dots, and nanowire composites. The challenges inherent to coupled electronic and thermal transport properties will be highlighted.

Disciplines:

• Science and Technology  / Nanotechnology