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 non-radiative recombination. Here we assess the trap-limited conversion efficiency of Sb2S3 by investigating non-radiative 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 efficiency of Sb2S3 to 16% light to electricity. 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.