A research team led by Prof. ZHANG Jian at the Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, in collaboration with Prof. XIAO Chong from the University of Science and Technology of China and Prof. ZHANG Yongsheng from Qufu Normal University, achieved a peak ZT value of 2.03 at 873 K in chalcopyrite-based thermoelectric materials using a novel dual antisite defect strategy.
Their findings were published in the Journal of the American Chemical Society.
In this study, the researchers developed a new Ag/In alloying strategy to introduce dual antisite defects in the Cu0.7Ag0.3Ga1-xInxTe2 thermoelectric system. These defects occured when certain atoms swapped positions in the crystal lattice, and they helped decouple the thermal and electrical transport processes. This allowed the material to conduct electricity more efficiently while blocking heat, overcoming a common challenge in thermoelectric design, where improving one property often compromised another.
They optimized the material composition to stabilize these defects. Silver and indium not only promoted defect formation but also reduced lattice distortion and encouraged a uniform solid solution, preventing phase separation. These structural modifications increased carrier concentration, maintained high carrier mobility, and enhanced the Seebeck coefficient, while also scattering heat-carrying vibrations (phonons) to significantly reduce thermal conductivity.
As a result, the optimized material Cu0.7Ag0.3Ga0.6In0.4Te2 achieved a peak ZT of 2.03 at 873 K and an average ZT of 0.61 over 300–873 K, representing roughly a 59% improvement compared with the original CuGaTe2.
This work demonstrates a new way to engineer high-performance thermoelectric materials, showing that carefully designed defects can overcome typical trade-offs and enable more efficient energy conversion.
Charge-Neutral antisite defect pairs for decoupled electron-phonon Transport (Image by XU Ting)