Design and discovery of a novel half-Heusler transparent hole conductor made of all-metallic heavy elements

Transparent conductors combine two generally contradictory physical properties, but there are numerous applications where both functionalities are crucial. Previous searches focused on doping wide-gap metal oxides. Focusing instead on the family of 18 valence electron ternary ABX compounds that consist of elements A, B and X in 1:1:1 stoichiometry, we search theoretically for electronic structures that simultaneously lead to optical transparency while accommodating intrinsic defect structures that produce uncompensated free holes. This leads to the prediction of a stable, never before synthesized TaIrGe compound made of all-metal heavy atom compound. Laboratory synthesis then found it to be stable in the predicted crystal structure and p-type transparent conductor with a strong optical absorption peak at 3.36 eV and remarkably high hole mobility of 2,730 cm2 V−1 s−1 at room temperature. This methodology opens the way to future searches of transparent conductors in unexpected chemical groups. Materials that are both electrically conducting and transparent to light are vital for optoelectronic devices, but are rare. Here, the authors perform a quantum mechanical search for such materials and identify the compound TaIrGe as an unexpected possibility, which they then synthesize.