High Thermoelectric Performance in Earth‐Abundant Cu₃SbS₄ by Promoting Doping Efficiency via Rational Vacancy Design

Abstract Sulfides are well investigated as thermoelectric materials but their performance is typically limited by low electrical conductivity. High electrical performance in Cu₃SbS₄ is reported by creating high valence vacancies, which efficiently provides multiple carriers. It is revealed from the perspective of a chemical bond by calculations that Al can serve as vacancy stabilizer as its entry into the lattice forms intensified bonds with neighboring atoms and lowers the vacancy formation energy. As a result, the average power factor of Cu₃SbS₄ with 9 wt% CuAlS₂ reaches 16.1 µW cm⁻¹ K⁻². Finally, by further addition of AgAlS₂, a peak zT of 1.3 and an average zT of 0.77 are obtained due to the reduced thermal conductivity. The attained average power factor and average zT are superior to other low‐toxic thermoelectric sulfides. The findings shed light on the new strategy for creating favorable vacancies to realize high‐efficiency doping in thermoelectric materials.