Transparent oxides are essential building blocks to many technologies, ranging from components in transparent electronics, transparent conductors, to absorbers and protection layers in photovoltaics and photoelectrochemical devices. However, thus far
, it has been difficult to develop p-type oxides with wide band gap and high hole mobility; current state-of-art transparent p-type oxides have hole mobility in the range of < 10 cm$^2$/Vs, much lower than their n-type counterparts. Using high-throughput computational screening to guide the discovery of novel oxides with wide band gap and high hole mobility, we report the computational identification and the experimental verification of a bismuth-based double-perovskite oxide that meets these requirements. Our identified candidate, Ba$_2$BiTaO$_6$, has an optical band gap larger than 4 eV and a Hall hole mobility above 30 cm$^2$/Vs. We rationalize this finding with molecular orbital intuitions; Bi$^{3+}$ with filled s-orbitals strongly overlap with the oxygen p, increasing the extent of the metal-oxygen covalency and effectively reducing the valence effective mass, while Ta$^{5+}$ forms a conduction band with low electronegativity, leading to a high band gap beyond the visible range. Our concerted theory-experiment effort points to the growing utility of a data-driven materials discovery and the combination of both informatics and chemical intuitions as a way to discover future technological materials.
The development of high performance transparent conducting oxides (TCOs) is critical to many technologies from transparent electronics to solar cells. While n-type TCOs are present in many devices, current p-type TCOs are not largely commercialized a
s they exhibit much lower carrier mobilities, due to the large hole effective masses of most oxides. Here, we conduct a high-throughput computational search on thousands of binary and ternary oxides and identify several highly promising compounds displaying exceptionally low hole effective masses (up to an order of magnitude lower than state of the art p-type TCOs) as well as wide band gaps. In addition to the discovery of specific compounds, the chemical rationalization of our findings opens new directions, beyond current Cu-based chemistries, for the design and development of future p-type TCOs.
