Efficient near room temperature thermoelectric cooling and power generation with CuAgSe

CuAgSe-based materials are attractive for low-temperature thermoelectric (TE) applications but are limited by bipolar conduction and relatively high thermal conductivity. Herein, we report a ligand-free aqueous synthesis of Te-doped CuAgSe (CuAgSe1-xTex), where structural and electronic modulation improve carrier transport and suppress phonon propagation. Ex-situ time-resolved X-ray diffraction reveals a spontaneous growth mechanism, while density functional theory calculations show that Te-5s and 5p orbitals hybridization generates localized states and an asymmetric density of states, thereby enhancing the Seebeck coefficient. Electron microscopy and strain analyses confirm that Te-doping introduces a high density of lattice dislocations and grain boundaries, leading to a reduced lattice thermal conductivity of 0.11 W m−1K−1 at 443 K. These synergistic effects translate into device-level performance—the first integrated CuAgSe thermoelectric modules, exhibit a maximum cooling temperature difference of 27.3 K, and power density of 0.34 W cm−2 with a conversion efficiency of 3.6% at a modest temperature gradient of 136 K. These results demonstrate that CuAgSe1-xTex enables efficient energy harvesting and localized cooling under small temperature gradient, underscoring the importance of structural and electronic design beyond conventional zT benchmarks.