Enhancing Thermoelectric Performance of n-Type PbSe through Forming Solid Solution with PbTe and PbS

As an inexpensive and earth abundant analogue of PbTe, PbSe has aroused growing attention recently as advanced thermoelectric materials. In the present report, the effect of PbTe and PbS co-alloying on the thermoelectric properties of n-type Pb0.99Sb0.01Se was systematically studied. PbTe and PbS are completely soluble in PbSe matrix, rendering strong phonon scattering because of reinforced lattice disorder. A minimal lattice thermal conductivity of ∼0.5 W m–1 K–1 at 823 K was successfully obtained for Pb0.99Sb0.01Se0.84Te0.08S0.08, which is ∼25% less than that of the Pb0.99Sb0.01Se control sample. Moreover, PbTe and PbS co-alloying leads to a reduced electron carrier concentration of Pb0.99Sb0.01Se, probably arising from the amphoteric dopant nature of Sb in PbTe. As a result, the Seebeck coefficient of Pb0.99Sb0.01Se is notably enhanced by co-alloying with PbTe and PbS, partly compensating the loss the carrier mobilities due to point defect scattering. Altogether, a maximal thermoelectric figure of merit ZT ∼ 0.9 at 823 K is attained in the Pb0.99Sb0.01Se0.68Te0.16S0.16 compound, which is nearly a 40% improvement over the control sample of Pb0.99Sb0.01Se.