Revealing composition and structure dependent deep-level defect in antimony trisulfide photovoltaics.

Antimony trisulfide (Sb2S3) is a kind of emerging light-harvesting material with excellent stability and abundant elemental storage. Due to the quasi-one-dimensional symmetry, theoretical investigations have pointed out that there exist complicated defect properties. However, there is no experimental verification on the defect property. Here, we conduct optical deep-level transient spectroscopy to investigate defect properties in Sb2S3 and show that there are maximum three kinds of deep-level defects observed, depending on the composition of Sb2S3. We also find that the Sb-interstitial (Sbi) defect does not show critical influence on the carrier lifetime, indicating the high tolerance of the one-dimensional crystal structure where the space of (Sb4S6)n ribbons is able to accommodate impurities to certain extent. This study provides basic understanding on the defect properties of quasi-one-dimensional materials and a guidance for the efficiency improvement of Sb2S3 solar cells.