Theory-driven design of hole-conducting transparent oxides

The design of {\em p}-type transparent conducting oxides (TCOs) aims at {\em simultaneously} achieving transparency and high hole concentration and hole conductivity in one compound. Such design principles (DPs) define a multi-objective optimization problem that is to be solved by {\em searching} a large set of compounds for optimum ones. Here, we screen a large set of ternary compounds, including Ag and Cu oxides and chalcogenides, by calculating via first-principles methods the design properties of each compound, in order to search for optimum {\em p}-type TCOs. We first select Ag$_{3}$VO$_{4}$ as a case study of the application of {\em ab-initio} methods to assess a compound as a candidate {\em p}-type TCO. We predict Ag$_{3}$VO$_{4}$ (i) to have a hole concentration of $\approx 10^{14}$ $cm^{-3}$ at room temperature, (ii) to be at the verge of transparency, and (iii) to have lower hole effective mass than the prototype {\em p}-type TCO CuAlO$_{2}$. We then map the hole effective mass $vs.$ the band gap in the selected compounds and determine those that best meet the DPs by having simultaneously minimum effective mass and a band gap large enough for transparency.