Cobalt sulfide thin film as an efficient counter electrode for dye-sensitized solar cells

The power conversion efficiency of dye sensitized solar cells (DSSCs) was improved using a nano rose petal like structured cobalt sulfide (CoS ₂) counter electrode (CE) with an iodine triiodide (I ^-/I₃^-) electrolyte. The CoS₂ nano rose petals like structure with a mean film thickness of 280 nm prepared using a solution containing 0.1 M cobalt chloride, 0.8 M urea and 0.8 M thioacetamide by inexpensive chemical bath deposition at 80 °C for 3 h resulted in an improved fill factor, short circuit current and open circuit voltage compared to the Pt electrodes. Tafel polarization and electrochemical impedance spectroscopy showed that CoS₂ electrode has smaller charge transfer resistance than Pt electrodes. DSSC fabricated with the CoS₂ CE achieved a power conversion efficiency of 5.32% under 1 sunlight illumination (100 mW cm^-2, AM 1.5 G), which surpassed that of the device based on Pt (5.02%).