Engineering Low-Dimensional Cu2–xS for Superior Thermoelectric Performance

In the field of thermoelectric materials, the design of low-dimensional structures has emerged as a prominent area of research. Low-dimensional thermoelectrics enhance performance by exploiting quantum confinement to optimize electronic states and size effects to reduce the thermal conductivity, thereby improving the power factor (PF) without compromising the Seebeck coefficient and electrical conductivity. Here, we successfully prepared two-dimensional (2D) Cu_2–xS thin films of varying thicknesses through magnetron sputtering. The thinnest 37 nm sample exhibits excellent thermoelectric properties at 500 K with a PF of 573.15 μW m^–1 K^–2, which represents the record among all Cu_2–xS-based thin-film materials to date. Moreover, there is a significant discrepancy between the thin films and the present work bulk Cu₂S material PF of 13.5 μW m^–1 K^–2. Additionally, the sample’s thermal conductivity and thermoelectric figure of merit (ZT) are 1.5 Wm^–1 K^–1 and 0.22, respectively, at 500 K. These findings underscore the potential of the quantum size effect in enhancing thermoelectric efficiency and offer a promising avenue for advancing the study of thermoelectric materials in energy conversion applications.