Origin of Broadband Emission and Large Stokes Shift in Antimony Trisulfide

The antimony trisulfide (Sb2S3) has been theoretically predicted to have various merits in exploiting high-performance thin-film solar cells and attracted intense attention. However, the power conversion efficiency of Sb2S3-based solar cells is yet to be satisfactory in experiments and the origin of large open circuit voltage (V-OC) loss is still a controversial question. Based on first-principles calculations, we have systematically analyzed the excited state behavior and dynamics images of carriers in Sb2S3 materials. Our calculations showed that intrinsic defects like vacancy (V-Sb and V-S) and antisites (Sb-S and S-Sb) are energetically accessible. More importantly, we found that the sulfide vacancy-bound excitons can produce a large Stokes shift of similar to 0.66 eV, which could well rationalize the experimental observations like the reduction of V-OC. These new findings suggest that the performance of Sb2S3-based solar cells might be largely enhanced by avoiding sulfide vacancy defects.

Automated summary

The excited state behavior and dynamics of carriers in Sb2S3 materials were systematically analyzed using first-principles calculations. Intrinsic defects such as sulfide vacancies were found to cause a large Stokes shift, leading to a reduction in the efficiency of solar cells.