Thermoelectric Performance Enhancement in Off-Stoichiometric Ag-Se Alloys via Composition Imbalance and Vacancy Suppression

This study investigates the thermoelectric performance of off-stoichiometric Ag-Se alloys through composition-imbalance engineering. By varying the Ag-to-Se ratio, we successfully tuned the carrier concentration and mobility by suppressing Se-vacancy formation and reducing electron scattering. Simultaneously, grain refinement induced by excess Se enhanced phonon scattering, thereby lowering the thermal conductivity. Structural and phase analyses confirmed that Ag₂Se remained the dominant phase across compositions. These findings highlight composition imbalance as a simple yet effective strategy for tuning thermoelectric performance in Ag-Se systems. This work offers a new pathway for designing high-performance, low-temperature thermoelectric materials.