Amphoteric Cu‐Doping Leading to High Thermoelectric Performance in p ‐Type Bismuth Antimony Telluride
Moritz Thiem, Zhiyuan Li, Minsu Heo, Fangyi Hu, Tian Lan, Youngdeog Koh, Ruiwen Xie, Chuanmu Tian, Marc Widenmeyer, Hyun‐Sik Kim, Jan P. Hofmann, Yuan Yu, Hongbin Zhang, Anke Weidenkaff, G. Jeffrey Snyder, Wenjie XieABSTRACT
The role of copper in Bi 2 Te 3 ‐based thermoelectric materials is not well understood, and there are conflicting results regarding its impact on thermoelectric properties. Some reports claim Cu is an electron donor after intercalating into the van der Waals‐like gap of (Bi,Sb) 2 Te 3 , while others show it acting as an acceptor. Here, we help clarify this discrepancy experimentally and theoretically by demonstrating that Cu behaves as an amphoteric dopant (acceptor or donor) governed by its processing pathway. While kinetic pathways allow for Cu intercalation into the van der Waals‐like gaps and electron donor behavior, thermodynamic equilibrium favors the substitution of Cu for Bi or Sb cations and acceptor behavior, which provides stronger chemical bonding and stability compared to intercalated Cu. When prioritizing thermodynamic stability, p ‐type Cu x Bi 0.5 Sb 1.5 Te 3 exhibits high near‐room‐temperature zT values, with the best‐performing composition among the investigated series reaching zT ≈1.36 ± 0.06 for four independently prepared x = 0.0025 samples. This arises from simultaneous improvements in both electronic properties (weighted mobility) and thermal properties (lattice thermal conductivity). Such improvements in zT for p ‐type (Bi,Sb) 2 Te 3 in consistently manufactured materials would greatly benefit many applications for solid‐state Peltier coolers and thermoelectric generators.