Additive-Assisted Hydrothermal Growth Enabling Defect Passivation and Void Remedy in Antimony Selenosulfide Solar Cells

Antimony selenosulfide, Sb₂(S,Se)₃, has recently emerged as a promising light-absorbing material due to its tunable photovoltaic properties, low toxicity, and robust environmental stability. However, despite these advantages, the current record efficiency for Sb₂(S,Se)₃ solar cells significantly lags behind their Shockley-Queisser limit, especially when compared to other well-established chalcogenide-based thin-film solar cells, such as CdTe and Cu(In,Ga)Se₂. This underperformance primarily arises from the formation of unfavorable defects, predominately located at deep energy levels, which act as recombination centers, thereby limiting the potential for performance enhancement in Sb₂(S,Se)₃ solar cells. Specifically, deep-level defects, such as sulfur vacancy (V_S), have a lower formation energy, leading to severe non-radiative recombination and compromising device performance. In recent years, my research group has continually improved power conversion efficiency of antimony selenosulfide via fine control of additional Se flux during the absorber preparation, rear surface passivation by post-deposition Se treatment, and tailoring bandgap grading by a hybrid growth approach. Most recently, we introduced thioacetamide (TA), a sulfur-containing additive, into the precursor solution for the hydrothermal deposition of Sb₂(S,Se)₃. Our results indicate that the incorporation of TA helps in passivating deep-level defects such as sulfur vacancies and in suppressing the formation of large voids within the Sb₂(S,Se)₃ absorber. Consequently, Sb₂(S,Se)₃ solar cells, with reduced carrier recombination and improved film quality, achieved a power conversion efficiency of 9.04%, with notable improvements in open-circuit voltage and fill factor. This work provides deeper insights into the passivation of deep-level donor-like V_S defects through the incorporation of a sulfur-containing additive, highlighting pathways to enhance the photovoltaic performance of Sb₂(S,Se)₃ solar cells.