Dual-Antisite Defects and Domain Structures Synergistically Boosting a Record-High ZT > 2.0 in Chalcopyrite Cu0.7Ag0.3Ga1-xInxTe2(x = 0-0.5).

Antisite defects, as intrinsic point defects in crystals, have demonstrated significant potential in optimizing the thermoelectric performance of materials, particularly by modulating the carrier concentration. However, they typically degrade carrier mobility due to the strong coupling among thermoelectric parameters. To address this limitation, we propose a dual-antisite defects strategy: by introducing donor-acceptor defect pairs to form electrically neutral configurations, carrier scattering can be significantly reduced due to charge compensation. Meanwhile, the presence of these point defects still maintains strong phonon scattering. This approach minimizes the loss of electrical mobility while effectively suppressing lattice thermal conductivity (κL). Using chalcopyrite CuGaTe2 as a matrix, we incorporated charge-balanced dual-antisite defects (AgGa″ and InCu··) via alloying. This type of electrically neutral dual-antisite defects can maintain carrier mobility while increasing carrier concentration and significantly suppresses κL by enhancing phonon scattering through the interaction between alloy disorder scattering induced by In alloying and nanodomains. Remarkably, in Cu0.7Ag0.3Ga0.6In0.4Te2, a record-high ZT value of 2.03 at 873 K was achieved. This dual-antisite defects strategy provides a new paradigm for defect engineering in thermoelectric materials, enabling the simultaneous optimization of electrical and thermal transport properties and offering a valid pathway toward high-performance thermoelectrics.