Sulfur Vacancies Limit the Open-Circuit Voltage of Sb₂S₃ Solar Cells

Antimony sulfide (Sb₂S₃) is a promising candidate as an absorber layer for single-junction solar cells and the top subcell in tandem solar cells. However, the power conversion efficiency of Sb₂S₃-based solar cells has remained stagnant over the past decade, largely due to trap-assisted nonradiative recombination. Here we assess the trap-limited conversion efficiency of Sb₂S₃ by investigating nonradiative carrier capture rates for intrinsic point defects using first-principles calculations and Sah-Shockley statistics. Our results show that sulfur vacancies act as effective recombination centers, limiting the maximum light-to-electricity efficiency of Sb₂S₃ to 16%. The equilibrium concentrations of sulfur vacancies remain relatively high, regardless of growth conditions, indicating the intrinsic limitations imposed by these vacancies on the performance of Sb₂S₃.