Strain‐Mediated Lattice Rotation Design for Enhancing Thermoelectric Performance in Bi₂S₂Se

Abstract A unique strain‐mediated lattice rotation strategy is introduced via nanocompositing to upsurge the optimized limits in the composition‐to‐structural pathway on rationally engineering the efficient thermoelectric material. In this study, a special lattice rotation via strain engineering is realized to optimize the desired electronic and chemical environment for enhancing thermoelectric properties in n‐type Bi₂S₂Se. This approach results in a unique transport phenomenon to assist high‐energy electrons in transferring through the optimized transport channels, and appropriate structure disparity to significantly localize phonons. As a result, Sb over Cl doping in Bi₂S₂Se gently reduces E_g and introduces defect states in bandgap with shifting down the Fermi level, thus causing increase in carrier concentration, which contributes to a higher power factor of ≈7.18 µW cm⁻¹ K⁻² (at T = 773 K). Besides, a lower thermal conductivity of ≈0.49 W m⁻¹ K⁻¹ is driven through lattice strain and defect engineering. Consequently, an ultra‐high ZT_max = 1.13 (at T = 773 K) and a high ZT_ave = 0.54 (323 K‐773 K) are realized. This study not only leads to an extraordinary thermoelectric performance but also reveals a unique paradigm for electron transportation and phonon localization via lattice strain engineering.