Self-Tuning the Carrier Concentration of PbTe/Ag_2 Te Composites with Excess Ag for High Thermoelectric Performance

Thermoelectric materials can be optimized by tuning the carrier concentration with chemical doping. However, because the optimum dopant concentration typically increases with temperature, the optimum efficiency can not normally be achieved for a uniform material in a temperature gradient. Here, we show Ag-doped PbTe/Ag_2Te composites exhibit high thermoelectric performance (∼50% greater than La-doped composites) because of a temperature induced gradient in the doping concentration caused by the temperature-dependent solubility of Ag in the PbTe matrix. This demonstrates a new mechanism to achieve a higher thermoelectric efficiency afforded by a given material system, and should be applicable to other thermoelectric materials.