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

Abstract

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 ∼1.2 at 773 K, and an average value of ∼1.1 over a range from 523 K to 823 K have been achieved for the Pb_0.99Ag_0.01Se sample. These findings, combined with the energy- and time-saving fabrication process, highlight the prospective commercialization of PbSe-based thermoelectric materials in the future.