Upper efficiency limit of Sb₂Se₃ solar cells

Antimony selenide (Sb₂Se₃) is at the forefront of an emerging class of sustainable photovoltaic materials. Despite notable developments over the past decade, the light-to-electricity conversion efficiency of Sb₂Se₃ has reached a plateau of ∼10%. Is this an intrinsic limitation of the material, or is there scope to rival the success of metal halide perovskite solar cells? Here, we assess the trap-limited conversion efficiency of Sb₂Se₃. First-principles analysis of the hole and electron capture rates for point defects in the bulk material demonstrates the critical role of vacancies as active recombination centers. We predict an upper limit of 26% efficiency in Sb₂Se₃ grown under optimal equilibrium conditions where the concentrations of charged vacancies are minimized. We further reveal how the detrimental effect of Se vacancies can be reduced by extrinsic oxygen passivation, highlighting a pathway to achieve high-performance metal selenide solar cells close to the single-junction thermodynamic limit.