Synergistic Enhancement of Thermoelectric Performance of n-type PbTe by Resonant Level and Single-atom-layer Vacancies

Modulating electrical and thermal transport through zero-dimensional point defects and one-dimensional dislocations are extensively investigated. However, the systematic study of exploring single-atom-layer vacancies for improving thermoelectric (TE) performance remains rare. In this study, we modulate the number density of single-atom-layer two-dimensional (2D) Te vacancies in lead telluride (PbTe) for the first time through bismuth and indium doping. DFT calculations reveal (Bi, In) co-doping lowers the formation energy of such defects, confirming the feasibility of this method. 2D Te vacancies simultaneously enhanced phonon scattering and evoked bond softening, significantly lowering the lattice thermal conductivity. Meanwhile, indium doping generates resonant level in the energy band, which increases the carrier concentration without deteriorating the Seebeck coefficient drastically. As a result, a peak TE figure of merit (zT) of ~1.6 and an average zT (zTavg) of 1.17 are achieved in the (Bi, In) co-doped PbTe. Furthermore, a high efficiency of 6.5% is obtained for the fabricated 2-pair module at a temperature difference of 500 K.