Excessively Doped PbTe with Ge-Induced Nanostructures Enables High-Efficiency Thermoelectric Modules

The application of thermoelectrics in waste heat recovery requires high conversion efficiency, which is best achieved through the combination of progressive performance-enhancing strategies. In this study, we combined engineered doping, nanostructuring, and module fabrication in PbTe-based thermoelectrics to generate high-ZT materials along with high-efficiency modules. The use of excess Na (4%) as a p-type dopant greatly enhanced the thermoelectric power factor by generating extra charge carriers at high temperature. The addition of minute amounts of Ge (<= 1%) generated nanoprecipitates, which greatly reduced the lattice thermal conductivity. An optimal ZT of similar to 1.9 at similar to 805 K was achieved for Pb0.953Na0.040Ge0.007Te as a p-type leg, which was combined with PbTe0.9964I0.0036 as an n-type leg to fabricate thermoelectric modules. An exceptionally high efficiency of similar to 12% for a temperature difference of 590 K was obtained in a cascade Bi2Te3/nanostructured PbTe module with eight p-n pairs.