Defect Engineering for Realizing p-Type AgBiSe₂with a Promising Thermoelectric Performance

Realization of ambipolar doping (n- and p-type) in thermoelectric materials is highly critical for module design. However, many thermoelectric materials can only be doped into one type, due to the Fermi-level pinning by intrinsic defects, or have poor performance for one doping type. AgBiSe2 is a typical case that shows persistent n-type doping while p-type AgBiSe2 has been predicted to exhibit higher thermoelectric performance but has not been reliably obtained nor has the performance been demonstrated. Here, we demonstrate the successful experimental synthesis of p-type AgBiSe2 by suppressing Se vacancies via adding an excess amount of Se. In addition, we show that Pb doping at the Bi site can effectively increase the hole concentration and optimize the power factor of p-type AgBiSe2. This leads to promising thermoelectric performance close to room temperature. Our work demonstrates the importance of defect engineering for overcoming the doping bottleneck, thus promoting the discovery of new thermoelectric materials.