The calculated self-consistent Fermi levels and defect/electron concentrations upon F doping are presented as functions of annealing temperature in Figure and and after cooling are mostly similar. The self-consistent Fermi level E F at room temperature is predicted to lie at 0.14 eV above the conduction band, assuming an annealing temperature of 600 • C. The electron concentration at this predicted E F reaches 10 19 cm -3 , which is around 1 order of magnitude higher than the Mott Criterion. At this carrier concentration, the predicted mobility and conductivity of F-doped Sb 2 O 5 is around 103 cm 2 V -1 s -1 and 100 S cm -1 respectively at room temperature, where the limiting scattering mechanism is mainly polar-optical phonon (POP) (Figure ). In comparison to conventional n-type TCOs, this predicted conductivity for F-doped Sb 2 O 5 is somewhat modest. If a greater conductivity is desired, a higher annealing temperature can be used as demonstrated in Figure , or potentially non-equilibrium growth conditions, where more fluorine can be incorporated to yield higher carrier concentrations. Moreover, the neglect of temperature-dependent renormalisation of the host band gap may also contribute to a slight underestimation of the equilibrium electron concentrations under F-doping here. The calculation is also limited by the relatively simple model used in the amset package to address impurity scattering, as the effect of a relatively significant F O concentration on the lattice is not explicitly accounted for in the carrier mobility model. Overall, the low-energy formation of resonant F O defects is predicted to push the self-consistent Fermi level into the conduction band, yielding a strongly degenerate semiconducting behavior upon F-doping in Sb 2 O 5 . The electronic band alignment of Sb 2 O 5 was investigated and compared with existing TCOs, shown in Figure . The ionization potential (IP) and the electron affinity (EA) were calculated to be 9.89 and 6.80 eV, respectively. The EA of Sb 2 O 5 is significantly larger than that of established TCOs. This is because the Sb 5s states mainly contribute to the CBM, as for ZnSb 2 O 6 and similar to other TCOs where the cation ns orbitals comprise the CBM. However, the ns energy levels differ due to the effective nuclear charge and the electron shielding effects. Other conventional post-transition metals have higher energy for the unoccupied ns states since they have lower oxidation states (+2/+3/+4) than Sb(V), and thus reduced nuclear attraction. Therefore, the Sb 5s orbitals in the +5 oxidation state have a smaller nuclear-electron distance, which has less shielding and stronger attraction, causing the Sb s states to sit at lower energy. Indeed, the 5 th ionization energy of Sb is much higher than the 4 th and the 3 rd ionization energies of Sn and In.