Defect formation of CuI-doped by group-IIB elements

First-principles calculations have been performed to investigate the doping defects in CuI with group-IIB elements such as Zn, Cd and Hg. The calculated transition energies for substitutional Zn, Cd and Hg are 1.32, 1.28 and 0.60 eV, respectively. These group-IIB elements at the substitutional sites complex with a copper vacancy (V-Cu) have the lower formation energies as compared to dopants located at the substitutional sites or interstitial sites, respectively. Among all the complex defects considered, [H-gCu + V-Cu] has the lowest formation energy and it induces the acceptor level epsilon(0/-) = 0.18 eV above the valence-band maximum (VBM), which is close to the acceptor level epsilon(0/-) = 0.1 eV of V-Cu, suggesting that Hg may be a good dopant for CuI to improve its p-type conductivity.