GW quasiparticle band structures of stibnite, antimonselite, bismuthinite, and guanajuatite

We present first-principles calculations of the quasiparticle band structures of four isostructural semiconducting metal chalcogenides A(2)B(3) (with A = Sb, Bi and B = S, Se) of the stibnite family within the G(0)W(0) approach. We perform extensive convergence tests and identify a sensitivity of the quasiparticle corrections to the structural parameters and to the semicore d electrons. Our calculations indicate that all four chalcogenides exhibit direct band gaps, if we exclude some indirect transitions marginally below the direct gap. Relativistic spin-orbit effects are evaluated for the Kohn-Sham band structures, and included as scissor corrections in the quasiparticle band gaps. Our calculated band gaps are 1.5 eV (Sb2S3), 1.3 eV (Sb2Se3), 1.4 eV (Bi2S3), and 0.9 eV (Bi2Se3). By comparing our calculated gaps with the ideal Shockley-Queisser value we find that all four chalcogenides are promising as light sensitizers for nanostructured photovoltaics.