Cobalt sulfide counter electrode using hydrothermal method for quantum dot-sensitized solar cells

• Efficient optimized CoS2 counter electrode for quantum dot sensitized solar cell.
• Cobalt sulfide shows better charge transfer kinetics and superior electro-catalytic activity than the conventional Pt.
• The power conversion efficiency of 2.27% with CoS2 CE based QDSSCs.

Chalcogenides are potential alternatives to platinum (Pt) based counter electrode (CE). This study reports cobalt sulfide (CoS2) thin films as robust, high-performance, economical, earth-abundant CE for quantum dot-sensitized solar cells (QDSSCs). CoS2 thin film has been deposited on a fluorine-doped tin oxide substrate by a hydro thermal method using 3-mercapto propionic acid and used as an efficient CE for polysulfide redox reactions in quantum dot-sensitized solar cells (QDSSCs). CdS/CdSe-sensitized QDSSCs exploiting CoS2 CE improved short-circuit photocurrent density and fill factor. We attained 2.27% solar light-to-electricity conversion efficiency, a value higher than reaped with Pt CE (1.73%). Electrochemical measurements testified that CoS2 reveals high electro-catalytic activity towards polysulfide reduction, thus accelerating QDSSCs performance. CoS2 also showed stability at a working state for over 10 h, resulting in highly reproducible performance, which is a serious challenge for solar cell.

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