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 (CoS2) 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%).