Influence of Sb inclusion on morphologies and carrier concentration properties of CTS thin films grown by sulfurization of Cu-Sn precursors

The impact of antimony (Sb) inclusion in Cu2SnS3 (CTS) films grown by sulfurization of Sb/Cu-Sn precursors and the growth mechanism of Sb-containing CTS were examined. The CTS grain size depended on the volume of the included Sb. During the sulfurization of the Cu-Sn precursor, S atoms first reacted with the Cu or Sn atoms and formed intermediate phases, such as CuS and SnS2. In addition, Sb acted to form a large-sized CuS grain during the low-temperature sulfurization up to 350 C. The excess Sb tended to form Sb2S3 during the sulfurization, most of which disappeared from the upper layer of the CTS films due to re-evaporation. The carrier concentration of the Sb-included CTS tended to decrease from compensation with Cu vacancies. The experimental results obtained in this study may serve as a first step toward achieving the high-quality large grain CTS thin films and high-efficiency CTS solar cells.