Low-Cost Solution Processed Nano Millet Like Structure CoS2 Film Superior to Pt as Counter Electrode for Quantum Dot Sensitized Solar Cells

Cobalt Sulfide (CoS2) counter electrodes (CE) with uniform size distribution were obtained on fluorine-doped tin oxide (FTO) substrate as counter electrodes for polysulfide redox electrolyte in CdS/CdSe/ZnS quantum dot-sensitized solar cells (QDSSCs) by chemical bath deposition (CBD) technique. In this study, we optimized the cobalt source, deposition temperature and time in the preparation of CoS2 thin film to achieve greater conversion efficiency with strong adhesion on FTO. Relative to the platinum (Pt) electrodes, the CoS2 electrode shows a higher catalytic activity, faster electron transport and lower charge-transfer resistance, which can play a role in rendering higher power conversion efficiency. As a result, QDSSCs with the optimized CoS2 CE achieved a higher short-circuit current density of 13.08 mA cm(-2), open-circuit voltage of 0.47 V, fill factor of 0.34 and overall photovoltaic conversion efficiency of 2.17% obtained under one sun illumination (100 mW cm(-2)). Therefore, CoS2CE can be used as a promising CE in QDSSCs with efficiency exceeding that of high-cost Pt-based cells (1.64%).