Chonnam National University is a South Korea-based public university that has reported resolving performance limitations in tin monosulfide thin-film solar cells. The approach is inserting a 7‑nanometer germanium oxide interlayer at the rear-contact interface. This GeOx layer is positioned between the molybdenum back contact and the SnS absorber. It has been formed via a vapor transport deposition process using natural oxidation of a thin germanium film. According to the researchers, the interlayer suppresses deep-level defects and blocks unwanted sodium diffusion. It also prevents formation of resistive molybdenum disulfide phases during high-temperature fabrication. These effects have improved the absorber quality and enhanced charge transport and collection. Device power conversion efficiency has increased from 3.71% in standard cells to 4.81% with the GeOx interlayer.​