Composite Engineering Facilitates High-Performance Cu2Se-GeTe Thermoelectrics.

Cu₂Se has emerged as a promising thermoelectric material due to its low lattice thermal conductivity, high Seebeck coefficient, and high peak figure of merit (ZT) at elevated temperatures. However, its performance is limited by a high intrinsic carrier concentration and low carrier mobility. In this work, we investigate Cu₂Se-based composites to overcome these challenges by introducing GeTe as compound phase to optimize carrier concentration, enhance mobility, and promote phonon scattering. The incorporation of GeTe significantly optimized both carrier concentration and mobility, with the Cu₂Se/5 wt % GeTe composite exhibiting a carrier mobility of 30.8 cm²·V^-1·s^-1, more than twice that of pristine Cu₂Se (11.4 cm²·V^-1·s^-1). Additionally, the inclusion of GeTe substantially reduced both the electrical and lattice thermal conductivity across the entire temperature range. These improvements culminated in a peak ZT of 2.2 at 923 K for the Cu₂Se/10 wt % GeTe composite. These findings underscore the effectiveness of utilizing high-performance thermoelectric materials, such as GeTe, as secondary phases to substantially boost the thermoelectric properties of Cu₂Se. This approach offers a promising pathway for the development of advanced thermoelectric materials for energy conversion applications.