I-doped Cu₂Se nanocrystals for high-performance thermoelectric applications

Cu₂Se is considered as a potential thermoelectric material due to its excellent electrical properties and relatively high ZT values. However, the temperature-dependent phase transition and expensive experimental preparation approach hamper its practical application. In this work, a series of Cu₂Se_1-xI_x (x = 0, 0.02, 0.03, 0.04, 0.05) alloys were prepared by using the cheap and facile hydrothermal method in combination with vacuum hot pressing. The crystal structures of synthesized Cu₂Se_1-xI_x (x ≤ 0.04) are identical to the cubic β-Cu₂Se. By doping with iodine, the thermoelectric figure of merit of Cu₂Se could be greatly improved up to 1.1 at 773 K and the phase transition temperature was reduced to 380 K. Our results suggest a promising route to optimize the performance of Cu₂Se-based materials for high performance thermoelectric applications.