Synergistically optimizing thermoelectric transport properties of n-type PbTe via Se and Sn co-alloying

We report n-type PbTe with a maximum ZT ∼1.2 at 673 K and an average ZT_ave ∼0.84 at 300–823 K, which was achieved through a Sn and Se co-alloying approach. We find that the lattice thermal conductivity can be largely reduced through introducing Se in Te sites, and the power factor can be enhanced through introducing Sn in the Pb sites. Combining two strategies via Se and Sn co-alloying in PbTe, results show that the lattice thermal conductivity at 300 K can be reduced from ∼3.1 Wm⁻¹K⁻¹ to ∼1.2 Wm⁻¹K⁻¹ after alloying 15% Se, which is consistent with the Callaway model. Meanwhile, we find that both carrier concentration and mobility can be enhanced through alloying small amount of Sn, which are supported by DFT calculation with emphasis on the defect formation energies. The improvement on electrical conductivity elucidates an enhanced power factor at 300 K increasing from ∼6.4 μWcm⁻¹K⁻² to ∼14.6 μWcm⁻¹K⁻². Through synergistically optimizing electrical and thermal transport properties of n-type PbTe via Sn and Se co-alloying, the ZT value is distinctly enhanced to 1.2 at 673 K, and the average ZT_ave value is improved by ∼35%, from ∼0.62 in PbTe_0.997I_0.003 to ∼0.84 in Pb_0.995Sn_0.005Te_0.847Se_0.15I_0.003, ensuring a high maximum thermoelectric conversion efficiency ∼10.7%.