Thermoelectric energy converters are solid state devices that convert thermal to electrical energy, and are used in heat pumps and power generators. They have no moving parts, conveying them the inherent advantages of compactness and robustness that have traditionally been offset by their low efficiency. This changed in the last decade when several classes of materials were developed with double the efficiency of commercial materials. Consequently, the new materials are poised to play a significant role in energy recovery applications from waste heat, and in new efficient air-conditioning schemes.
This talk will briefly review the new applications, as well as the recent materials design strategies used. Almost all the progress to date has come from reductions in thermal conductivity obtained using nanotechnologies or structural disorder. In 2008, we developed a new strategy based on resonant impurity doping, which doubled the efficiency of p-type PbTe, the semiconductor used in power generation around 500° C. We recently extended this approach to Bi2Te3, which is used in Peltier coolers. The physical mechanism underlying this improvement was originally developed for metals by Friedel, and is similar to the Kondo effect in dilute magnetic alloys.