The DFT supercell approach for calculating defects fails to properly model the bound states of resonant/shallow defects, as their large, delocalized wave functions extend far beyond the supercell length. Thus constraining these states to the supercell results in strong finitesize effects and spurious exciton-like interactions. However, several indicators can be used to determine that the defect is a true shallow state. For instance, we find the charge density of the V 0 Cu hole state to be delocalized across the supercell (Supporting Information Section 5), that the calculated (0/-1) transition level shifts toward the VBM with increasing supercell size, and lastly, that the atomic sites surrounding the vacancy differ in position by less than 0.01 Å between V -1 Cu and V 0 Cu . Indeed, using the screening methods developed by Kumagai et al., we find the V 0 Cu hole state to have similar orbital character to the bulk VBM, demonstrating its hydrogenic perturbed host state (PHS) nature. Therefore, despite the large predicted concentrations for copper vacancies (Table ), they will not play a role in non-radiative capture processes.