Mechanism of effect of intrinsic defects on electrical and optical properties of Cu2CdSnS4: an experimental and first-principles study

摘要

Near stoichiometric and Cd-poor Cu2CdSnS4 (CCTS) thin films with p-type conductivity were prepared by magnetron sputtering and post-sulfurizing. It is found that the hole concentration of the Cd-poor CCTS is two orders of magnitude higher than that of the near stoichiometric CCTS while its optical bandgap is smaller than the near stoichiometric CCTS'. It is suggested by using first-principles calculations that the dominant intrinsic defects are Cu vacancy (V-Cu) and fully passivated defect complex of 2Cu(Cd)+SnCd in the Cd-poor CCTS, but V-Cu and CuCd in the near stoichiometric CCTS. The V-Cu is responsible for the p-type conductivity of both CCTS films, while the 2Cu(Cd)+SnCd complex for smaller bandgap and higher hole concentration of the Cd-poor CCTS. The mechanism of effect of the intrinsic defects on the optical and electrical properties of the CCTS is suggested in the present paper.