Native p-type transparent conductive CuI via intrinsic defects

The ability of CuI to be doped p-type via the introduction of native defects has been investigated using first-principles pseudopotential calculations based on density functional theory. The Cu vacancy has a lower formation energy than any of the other native defects, which include I vacancy (VI), Cu interstitial (Cui), I interstitial (Ii), Cu antisite (CuI), and I antisite (ICu). Combined with its shallow acceptor level, it offers sufficient hole concentrations in CuI. The natural band alignments as compared to zinc-blende ZnS, ZnSe, and ZnTe have also been calculated in order to further identify the p-type dopability of CuI. It is found that CuI has a relatively high valence band maximum and conduction band minimum, which also makes it easy to dope CuI p-type in terms of the doping limit rule. In addition, the small effective mass of the light hole—about 0.303m0—can provide high mobility and p-type conductivity in CuI. All of these results make CuI an ideal candidate for native p-type materials