High Thermoelectric Performance in High-Entropy AgMnGePbSbTe₅ With Pb Vacancies

Thermoelectric materials enable the conversion of heat into electricity with no waste heat. Nanotwined AgMnGePbSbTe₅, a novel P-type narrow bandgap high-entropy semiconductor, exhibits enhanced thermoelectric performance upon the introduction of Pb vacancies. With increasing Pb vacancy content, the hole concentration rose monotonically, dramatically augmenting the electrical conductivity, thus enhancing the power factor. The DFT calculation indicates that electron band convergence herein improves the density of states effective mass, hence stabilizing the Seebeck coefficient. On the other hand, as the vacancies promote the point defect scattering, the lattice thermal conductivity is suppressed as well. Consequently, the synergistic effects on both electrical and thermal transport led to a peak ZT of 2.23 at 723 K and an average ZT of 1.31 across the temperature range of 303-813 K for AgMnGePb_0.97SbTe₅, representing improvements of 31% and 34% over the initial sample, respectively. This material creates a competitive thermoelectric performance among the Te-based thermoelectric materials, establishing a promising optimization strategy utilizing vacancy engineering.