Intrinsic and complex defect engineering of quasi-one-dimensional ribbons Sb2S3 for photovoltaics performance

Sb₂S₃ has attracted great attention recently as a prospective solar cell absorber material. In this work, intrinsic defects, dopants, and their complexes in Sb₂S₃ are systematically investigated by using hybrid functional theory. V_Sb and V_S are dominant native defects and pin the Fermi level near the midgap, which is consistent with the high resistivity observed experimentally. Both V_Sb and V_S introduce deep levels inside the band gap, which can trap free carriers. Our calculated deep transition levels of V_Sb and Sb_S are consistent well with the results of the deep-level transient spectroscopy measurement. We further study dopants (including Cu, Ti, Zn, Br, and Cl) in Sb₂S₃ and find that Zn and Br/Cl are shallow acceptors and donors, respectively, which may be used to control the carrier and trap densities in Sb₂S₃. In addition, the defect complexes, i.e., Cu(Zn)_Sb+V_S and Cl(Br)_S+V_Sb are also investigated. The interaction between the donor and acceptor defects makes the defect levels of complexes shallower and less detrimental to carrier transport.