Deciphering the Role of Key Defects in Sb₂Se₃, a Promising Candidate for Chalcogenide-Based Solar Cells

Herein, we report a thorough investigation on Sb2Se3, a promising absorber material for photovoltaic applications, using state of the art quantum methods to understand the impact of defects on its electrical properties. The results show that despite a rather small stability domain, Sb2Se3 is easy to synthesize because there is no other possible stable competing binary phase in the Sb/Se system. Our calculations prove that formation of intrinsic n-type defects is unlikely, because Sb vacancies restrain the Fermi level from reaching the CBM vicinity. In contrast, intrinsic p-type semiconductor behavior is expected because of the SbSe antisite defects. Doping is a commonly used technique to impact the charge carrier concentration as well as the charge carrier nature. In that context, several extrinsic defects were considered, based on tin and copper to enhance the native p-typeness, and halogenides (Cl, Br, I) to induce n-type doping in Sb2Se3. Our results tend to prove that Sb2Se3:Cu(p)/Sb2Se3:I(n) might be a viable homojunction for photovoltaic devices.