Frist-Principles Study on the Intrinsic Point Defects in the Quasi-One-Dimensional Photovoltaic Semiconductor Sb₂Se₃

As a novel thin-film solar cell absorber semiconductor, Sb₂Se₃ has attracted increasing attention recently and a 5.93% light-to-electricity conversion efficiency has been achieved. Different from the conventional covalent photovoltaic semiconductors such as CdTe, Cu(In,Ga)Se₂ and Cu₂ZnSn(S,Se)₄, Sb₂Se₃ is a quasi-one-dimensional material in which the [Sb₄Se₆]_n atomic-chains (ribbons) bind with each other through van der Waals forces. Here we studied the intrinsic point defects in Sb₂Se₃ using the density functional theory calculations with both the generalized gradient approximation and the hybrid functionals. In a Se-rich condition, the shallow acceptor, Se_Sb antisite, is the dominant defect with the lowest formation energy, accounting for the observed p-type conductivity, while in a Se-poor condition, Sb_Se and V_Se are the dominant donor defects. Those cation-replace-anion and anion-replace-cation antisite defects cannot form with high concentration in conventional covalent semiconductors, but they can be dominant in Sb₂Se₃. The results are weakly influenced by the functionals.