Enhancing thermoelectric performance of n-type PbTe through separately optimizing phonon and charge transport properties

The n-type PbTe still maintains relatively low thermoelectric performance compared with its p-type counterpart. Thus, to promote its performance in n-type PbTe, we conduct successive strategies that firstly suppressing the lattice thermal conductivity (κ_lat) through alloying with ternary compound AgSbSe₂, and then optimizing carrier density with Sb, Bi or I doping. In AgSbSe₂-alloyed PbTe samples, the κ_lat can be evidently reduced, and the minimum κ_lat decreases from ∼1.1 Wm⁻¹K⁻¹ in undoped PbTe to ∼0.8 Wm⁻¹K⁻¹ in PbTe–5%AgSbSe₂. Based on PbTe–5%AgSbSe₂ matrix, several dopants (Sb, Bi or I) are used to optimize its carrier density, and found that I element is verified to be the most effective dopant to enhance its electrical transport properties. In I-doped PbTe–5%AgSbSe₂ samples, the carrier density raises from ∼2.49 × 10¹⁶ cm⁻³ in PbTe–5%AgSbSe₂ to ∼1.15 × 10¹⁹ cm⁻³ in PbTe_0.992I_0.008-5%AgSbSe₂, which contributes to the maximum power factor ∼14.8 μWcm⁻¹K⁻². Combining the reduced lattice thermal conductivity and improved power factor, the maximum ZT_max and average ZT_ave values in PbTe_0.992I_0.008-5%AgSbSe₂ are boosted to ∼1.0 at 723 K and ∼0.77 at 300–823 K, respectively. This work points out a valid avenue to improve thermoelectric transport property in n-type PbTe with separately successive strategies to adjust its thermal and electrical performance.