Elucidating Defect Behaviors Optimizing the Thermoelectric Performance in PbTe-MgTe Based Materials

PbTe-MgTe based compounds have been demonstrated as promising medium-temperature thermoelectric materials, and significant research efforts have been devoted to enhancing their performance. However, previous studies have primarily focused on low MgTe concentrations (within the solubility limit of ~6 mol%), and a systematic understanding of intrinsic defect behaviors in the PbMgTe solid solution remains lacking. In this work, we perform high-throughput density functional theory calculations to systematically evaluate a comprehensive set of intrinsic defects (including vacancies, anti-sites, and interstitials) in the PbMgTe solid solution modeled by SQS. To the best of our knowledge, this is the first systematic defect study in the PbMgTe system at this composition. Our calculations reveal that vacancies (V_Pb, V_Mg, V_Te) and Mg interstitials (Mg_i) exhibit low formation energies, with acceptor and donor behaviors that effectively facilitate p-type and n-type conductivity, respectively. Notably, these defects induce modifications in the electronic structure that lead to a significant enhancement of the density of states (DOS) near the band edges. Consequently, the Seebeck coefficient is markedly improved compared to that of intrinsic PbMgTe. Our work not only provides valuable insights for defect engineering in PbMgTe-based materials but also establishes a mechanistic link between defect-induced DOS changes and thermopower enhancement, advancing beyond previous studies that focused primarily on formation energies. These findings help bridge the performance gap between n-type and p-type thermoelectric properties.