Unlocking High-Performance Te-Free p-Type Thermoelectrics via Cu Doping in Entropy-Engineered Cd_0.5Zn_0.5Sb Zintl

Zintl phases are crucial for Te-free power generation and electrical cooling modules, which are considered next-generation thermoelectric (TE) technology. While n-type Zintl materials, such as Mg₃Sb₂, have achieved remarkable performance, their p-type counterparts are restricted by electron-phonon coupling. This work demonstrates a cost-effective p-type CdSb-based Zintl material with high TE performance. We find that applying entropy engineering can sharply enhance the solid solubility of Cu in CdSb. Cu doping in entropy-engineered Cd_0.5Zn_0.5Sb raises carrier concentration. More importantly, Cu boosts carrier mobility to about 222 cm² V^-1 s^-1 by screening ionized impurity scattering and enhancing covalent bonding across the cleavage plane along the [1 0 0] direction. Additionally, Cu doping induces dislocation scattering and lattice softening, significantly reducing lattice thermal conductivity. As a result, the Cd_0.46Cu_0.04Zn_0.5Sb material achieves a high ZT of 1.5 at 573 K. Its high performance is verified by integrated TE devices. This work validates Cd_{1- x}Zn_xSb Zintl phases as highly efficient p-type TE materials for practical applications.