Matrix plainification leads to high thermoelectric performance in plastic Cu₂Se/SnSe composites

Thermoelectric technology exhibits significant potential for power generation and electronic cooling. In this study, we report the achievement of exceptional thermoelectric performance and high plasticity in stable Cu₂Se/SnSe composites. A novel matrix plainification strategy was employed to eliminate lattice vacancies within the Cu₂Se matrix of the Cu₂Se/SnSe composites, resulting in a marked improvement in carrier mobility and power factor. The presence of quasi-coherent interfaces induces phonon scattering, reducing lattice thermal conductivity without compromising carrier mobility. Consequently, a high figure of merit (ZT) of 3.3 was attained in the Cu₂Se/5 wt.% Sn_0.96Pb_0.01Zn_0.03Se composite. Additionally, the presence of high-density nanotwins imparts remarkable plasticity to the composite, yielding a compressive strain of 12%. The secondary phase contributes to the stability of the composite by hindering the extensive migration of Cu ions through bonding interactions. Our findings present a novel strategy for enhancing the thermoelectric performance of composite semiconductors, with potential applicability to other thermoelectric systems.