Resonant Doping in Binary Sb(V)-Oxide Sb2O5 for High-Mobility Transparent Conductors.

The development of earth-abundant transparent conducting oxides (TCOs) requires materials that combine high carrier concentrations with minimal degradation of electron mobility. Sb-(V)-based oxides have recently emerged as promising candidates owing to their highly dispersive Sb 5s-derived conduction bands and deep valence-band positions. While degenerate conductivity in Sb2O5 has previously been predicted through anion-site F substitution, the viability of resonant donor engineering on the cation sublattice remains unexplored. Here, using hybrid density functional theory and rigorous defect thermodynamics, we show that W acts as an effective resonant donor dopant when substituted on Sb sites in Sb2O5, whereas Mo exhibits only weak donor behavior due to the stabilization of the localized electronic state for the neutral charge state. Both WSb and MoSb exhibit low formation energies under n-type conditions, with W-doped Sb2O5 yielding an electron concentration exceeding 1 × 1019 cm-3 while Mo-doping results in a moderate value of around 1 × 1018 cm-3. Unfolded band structure analysis reveals that the W 5d and Mo 4d donor states reside well above the conduction band minimum and exhibit negligible hybridization with the Sb 5s states that govern transport. This preservation of the dispersive conduction band enables degenerate doping without significant perturbation of band curvature. These results establish resonant cation-site doping as a transferable design strategy in Sb-(V)-based oxides and broaden the chemical space for high-mobility, earth-abundant TCOs, while recognizing monoclinic Sb2O5 as an experimentally realized but synthetically challenging host material.