A novel p-type half-Heusler from high-throughput transport and defect calculations

In this work we identify p-type half-Heusler thermoelectric candidates using high-throughput techniques. Multiple descriptors are used to evaluate transport properties, elemental abundancies and thermodynamic stabilities. We identify the known (V/Nb/Ta)FeSb and (Zr/Hf)CoSb compounds as well as a novel encouraging (Nb/Ta)CoSn half-Heuslers system. We then use state of the art defect thermochemistry calculations to rule out any intrinsic doping limitations and thereafter predict extrinsic dopants for each candidates. We demonstrate that the defect calculations agree well with existing experiments for the known systems, where we also provide new routes to achieve p-doping. For the (Nb/Ta)CoSn system, group IV transition metals (Ti,Zr,Hf) are predicted as the specific dopant choices to realize their potential as high-performance p-type half-Heusler thermoelectrics. The electronic structure of the half-Heuslers are also analysed using molecular orbital theory to understand the origins of favorable p-type transport properties.