Optimization of Thermoelectric Properties and Physical Mechanisms of Cu2Se-Based Thin Films via Heat Treatment

Cu2Se is an attractive thermoelectric material due to its layered structure, low cost, environmental compatibility, and non-toxicity. These traits make it a promising replacement for conventional thermoelectric materials in large-scale applications. This study focuses on preparing Cu2Se flexible thin films through in situ magnetron sputtering technology while carefully optimizing key preparation parameters, and explores the physical mechanism of thermoelectric property enhancement, especially the power factor. The films are deposited onto flexible polyimide substrates. Experimental findings demonstrate that films grown at a base temperature of 200 °C exhibit favorable performance. Furthermore, annealing heat treatment effectively regulates the Cu element content in the film samples, which reduces carrier concentration and enhances the Seebeck coefficient, ultimately improving the power factor of the materials. Compared to the unannealed samples, the sample annealed at 300 °C exhibited a significant increase in room temperature Seebeck coefficient, rising from 9.13 μVK−1 to 26.73 μVK−1. Concurrently, the power factor improved from 0.33 μWcm−1K−2 to 1.43 μWcm−1K−2.