Realizing high thermoelectric performance in Ag-doped PbSe by morphology engineering

Efficient thermoelectric power generation requires a large applicable temperature range and correlated materials with outstanding dimensionless figure of merit values. Lead chalcogenides, especially PbTe-based materials, play a pivotal role in building thermoelectric devices for applications at intermediate temperature. However, the use of earth-scarce Te and the obstacles of achieving a high power factor and low thermal conductivity have limited progress in this field. Here, earth-abundant PbSe-based materials have been made by a simultaneous approach of combining self-propagating synthesis (SHS) and SPS techniques with optimized morphology engineering. Based on excess Ag doping and an ultrafast synthesis process, materials with parallel connections arising from enormous Ag2Se nanofibers with high hole mobility and Ag-doped PbSe with a small effective mass have been created, resulting in enhanced electrical properties. Meanwhile, multi-sized pores which modify the morphology have been formed during the reaction, leading to Ag-doped materials with low lattice thermal conductivity by reducing both the sound velocity and phonon mean free paths. Ultimately, a high figure of merit (ZT) of similar to 1.2 at 773 K, and an average value of similar to 1.1 over a range from 523 K to 823 K have been achieved for the Pb0.99Ag0.01Se sample. These findings, combined with the energy- and time-saving fabrication process, highlight the prospective commercialization of PbSe-based thermoelectric materials in the future. The ultrafast synthesis process combined with Ag doping gives rise to the formation of Ag2Se nanofibers and multi-sized pores. Subsequently, the high thermoelectric performance in Ag-doped PbSe can be achieved by morphology engineering.