Simultaneously optimized thermoelectric performance of n-type Cu2Se alloyed Bi2Te3

To achieve the optimized performance and the widespread application of thermoelectric materials, it is crucial to decouple the highly interrelated thermoelectric parameters of materials. In this study, we illustrate that phonon and carrier transport properties of n-type Bi2Te3-based composites can be simultaneously optimized through alloying Cu2Se. Owing to the chemical reactions between the Bi2Te3 matrix and the Cu2Se additives during the sample preparation, the carrier concentration and density-of-states effective mass can be tuned to optimize the carrier transport properties, while the lattice thermal conductivity can be reduced by introducing hierarchical structures including point defects, Cu7Te5 inclusions, phase boundaries and localized Te-deficient regions. As a result, an enhanced thermoelectric performance is achieved compared with pristine Bi2Te3. Our study indicates the alloying Cu2Se can synergistically control the thermoelectric properties of Bi2Te3.