Intrinsic and complex defect engineering of quasi-one-dimensional ribbons Sb 2 S 3 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. VSb and VS are dominant native defects and pin the Fermi level near the midgap, which is consistent with the high resistivity observed experimentally. Both VSb and VS introduce deep levels inside the band gap, which can trap free carriers. Our calculated deep transition levels of VSb and SbS 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+VS and Cl(Br)S+VSb are also investigated. The interaction between the donor and acceptor defects makes the defect levels of complexes shallower and less detrimental to carrier transport.