Realizing High Performance in P-Type SnBi₂Te₄ Through Synergistically Improving Effective Mass and Suppressing...

Thermoelectric materials, which facilitate the mutual conversion between thermal and electrical energy, offer a promising alternative for sustainable energy solutions. High-performance thermoelectric materials require excellent electrical conductivity and low thermal conductivity. Among emerging candidates, AB₂X₄ (A = Ge, Sn, Pb; B = Sb, Bi; X = Se, Te) compounds have garnered attention due to their unique septuple atomic layered crystal structure and poor lattice thermal conductivity. Here, the septuple atomic layered SnBi₂Te₄ is successfully synthesized and its thermoelectric performance significantly enhanced through isovalent elements alloying. The peak ZT ≈ 0.56 at 473 K and an average ZT ≈ 0.47 achieved over the temperature 300-673 K, which is 12 and 14 times higher than those in pristine SnBi₂Te₄. The incorporation of Sb and Se into p-type SnBi₂Te₄ system significantly improves thermoelectric performance through three synergistic mechanisms: 1) enhance the electrical conductivity via effective mass enlarging, 2) suppress the bipolar thermal diffusion through bandgap widening, and 3) reduce the lattice thermal conductivity by point defect scattering. The results demonstrate that isovalent elements alloying is an effective strategy to realize the promising high performance of septuple atomic layered p-type SnBi₂Te₄, which is applicable strategy for AB₂X₄ based compounds.