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 W_Sb and Mo_Sb 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.