High-Ranged ZT Value Promotes Thermoelectric Cooling and Power Generation in n-Type PbTe

Excellent thermoelectric cooling and power generation are simultaneously realized in an n-type PbTe-based thermoelectric material. The cooling temperature difference (ΔT) of ≈15.6 K, maximum power density of ≈0.4 W cm⁻² and conversion efficiency of ≈1.5% with T_C = 295 K and T_H = 765 K can be obtained in a single-leg device composed of PbTe-30%SnSe-1.5%Cu. This advanced thermoelectric performance in n-type PbTe-30%SnSe-1.5%Cu mainly originates from its high-ranged ZT value achieved through optimizing its bandgap, carrier density, and microstructure. The bandgap in PbTe is first reduced by SnSe alloying to facilitate the carrier transport properties at low temperature range (300–573 K). With further tuned carrier density, the average power factor increases from ≈10.2 µW cm⁻¹ K⁻² in Pb_0.985Sb_0.015Te-30%SnSe to ≈16.2 µW cm⁻¹ K⁻² in PbTe-30%SnSe-1.5%Cu at 300–773 K. Moreover, microstructure observation reveals high-density dislocations in PbTe-30% SnSe-1.5% Cu, which can dramatically suppress the room-temperature lattice thermal conductivity from ≈2.21 Wm⁻¹ K⁻¹ in Pb_0.985Sb_0.015Te to ≈0.53 Wm⁻¹ K⁻¹ in PbTe-30%SnSe-1.5%Cu. As a result, a room-temperature ZT value of ≈0.7 and high average ZT value (ZT_ave) of ≈0.98 can be obtained in PbTe-30%SnSe-1.5%Cu at 300–573 K, which makes its performance comparable to the commercial n-type Bi₂Te₃-based thermoelectric material.