High-Mobility Bismuth-based Transparent <i>p</i>-Type Oxide from High-Throughput Material Screening

Abstract

Transparent oxides are essential building blocks to many technologies,\nranging from components in transparent electronics, transparent conductors, to\nabsorbers and protection layers in photovoltaics and photoelectrochemical\ndevices. However, thus far, it has been difficult to develop p-type oxides with\nwide band gap and high hole mobility; current state-of-art transparent p-type\noxides have hole mobility in the range of &lt; 10 cm$^2$/Vs, much lower than their\nn-type counterparts. Using high-throughput computational screening to guide the\ndiscovery of novel oxides with wide band gap and high hole mobility, we report\nthe computational identification and the experimental verification of a\nbismuth-based double-perovskite oxide that meets these requirements. Our\nidentified candidate, Ba$_2$BiTaO$_6$, has an optical band gap larger than 4 eV\nand a Hall hole mobility above 30 cm$^2$/Vs. We rationalize this finding with\nmolecular orbital intuitions; Bi$^{3+}$ with filled s-orbitals strongly overlap\nwith the oxygen p, increasing the extent of the metal-oxygen covalency and\neffectively reducing the valence effective mass, while Ta$^{5+}$ forms a\nconduction band with low electronegativity, leading to a high band gap beyond\nthe visible range. Our concerted theory-experiment effort points to the growing\nutility of a data-driven materials discovery and the combination of both\ninformatics and chemical intuitions as a way to discover future technological\nmaterials.\n