Defect Reconfiguration in Hole-Doped PbSe via Minute Te Doping for Significantly Enhanced Thermoelectric Performance

Rich defects near the percolation threshold of dilute solid solutions are of fundamental interest to thermoelectric research. Sn-substituted Pb0.98Na0.02Se (1 mol %) is a typical example that demonstrates how various defects induce intriguing transport phenomena. Unfortunately, the presence of Pb vacancies severely degrades the carrier mobility of samples, and the thermoelectric figure of merit ZT is only marginally improved. In this study, we show that Pb vacancies are effectively inhibited by a facile defect reconfiguration strategy. This is achieved by doping a dilute amount of Te at Se sites of Pb0.97Sn0.01Na0.02Se, where the interstitial Sn ions are pulled back to Pb sites as revealed by the X-ray photoelectron spectroscopy analysis and the positron annihilation test. Consequently, Pb vacancies get occupied, and the room temperature carrier mobility is remarkably recovered from 2.8 to 70 cm2 V–1 s–1 upon 3 mol % Te doping. Moreover, Te doping reinforces phonon scattering by strain and mass field fluctuations. The lattice thermal conductivity at 300 K goes down to ∼1.7 W m–1 K–1 for Pb0.97Sn0.01Na0.02Se0.94Te0.06, which is ∼32% lower than that of the Pb0.97Sn0.01Na0.02Se control sample. Altogether, the average ZT value of Pb0.97Sn0.01Na0.02Se between 300 and 773 K is doubled upon 6 mol % Te doping.