A fully self-contained study of the thermodynamic and electronic properties of intrinsic point defects in the solar absorber materials CuInSe${}_2$ and CuGaSe${}_2$ based on screened-exchange hybrid density functional theory is presented. The results are partly at odds with data obtained within local density functional theory in former studies. ${\mathrm{Ga}}_{\mathrm{Cu}}$ electron traps as well as ${\mathrm{Cu}}_{\mathrm{In}}$ and ${\mathrm{Cu}}_{\mathrm{Ga}}$ hole traps are found to be the dominant intrinsic recombination centers. In contrast to the accepted view, complex formation of antisites with copper vacancies is not decisive for explaining the favorable properties of CuInSe${}_2$, since ${\mathrm{In}}_{\mathrm{Cu}}$ is already a shallow defect by itself. The localization of holes is observed on ${\mathrm{Cu}}_{\mathrm{In}}$ and ${\mathrm{Cu}}_{\mathrm{Ga}}$ as well as on ${\mathrm{V}}_{\mathrm{In}}$ and ${\mathrm{V}}_{\mathrm{Ga}}$ when supercells of 216 atoms are used. Furthermore, the results raise doubts about the relevance of selenium vacancies and DX centers for experimentally observed metastabilities. Finally, a guide to the optimal preparation conditions in terms of the point defect physics of CuInSe${}_2$ and CuGaSe${}_2$ for their application as solar cell absorbers is provided.

• Received 18 December 2012

DOI:https://doi.org/10.1103/PhysRevB.87.245203