Chemistry of defect induced photoluminescence in chalcopyrites: The case of CuAlS2

Hybrid exchange density functional theory is used to study the wide band gap chalcopyrite CuAlS2. The formation energies of charged and neutral intrinsic defects are calculated for different environmental conditions, and it is shown that CuAlS2 is a p-type material that cannot be type inverted through the formation of intrinsic defects. The calculated band gap states associated with the different intrinsic defects are used to comment on the origin of the observed CuAlS2 photoluminescence emissions. The origin and stability of ordered defect compounds derived from CuAlS2 are investigated, and it is concluded that CuAl5S8 is a stable ordered defect compound, albeit in a small region of phase space.