Non‐Bonding Element Doping Enables Weakened Electron‐Phonon Interaction and Superior Thermoelectric Performance in CuGaTe ₂

ABSTRACT Conventional thermoelectric materials suffer from a fundamental trade‐off between carrier concentration and mobility ascribed to the Coulomb scattering from ionized impurities under heavy doping. Here, we demonstrate a novel non‐bonding doping mechanism in Mg‐doped CuGaTe 2 with barely affected carrier mobility. Ultrafast dynamics analysis reveals a substantially reduced carrier scattering potential in Mg‐doped CuGaTe 2 compared to that doped by other dopants. First‐principles calculations show that Mg with only active s electrons, neither has bonding nor antibonding states with the orbitals of Te in the vicinity of valence band edge. Such unique non‐bonding character weakens the dependence of energy level on lattice deformation, resulting in suppressed electron‐phonon interactions. Consequently, the carrier mobility is enhanced by ∼100%, leading to a high average power factor of 1.66 mW m −1 K −2 . Further alloying Cu with Ag to reduce lattice thermal conductivity leads to a record‐high peak zT of 2.1 at 973 K and the highest reported average zT of 0.93 over 294–973 K. Our findings underscore the critical role of dopant orbital hybridization in tailoring electron‐phonon interactions, providing a rational doping strategy for high‐performance thermoelectric materials and other electronic materials that require high carrier mobility.