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

Abstract

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 (κlat) through alloying with ternary compound AgSbSe2, and then optimizing carrier density with Sb, Bi or I doping. In AgSbSe2-alloyed PbTe samples, the κlat can be evidently reduced, and the minimum κlat 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 PbTe0.992I0.008-5%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 ZTmax and average ZTave values in PbTe0.992I0.008-5%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.