Self-Assembled CoS2 Nanocrystal Film as an Efficient Counter Electrode for Dye-Sensitized Solar Cells

In pursuit low-cost and facile synthesis of counter electrode (CE) material as an alternative to expensive Pt for dye-sensitized solar cells (DSSCs), a new procedure for preparing CEs without any postannealing treatment is reported by using a self-assembly technique to obtain a stable thin film as the CE in DSSCs. The self-assembled CoS2 film is prepared via a facile two-step approach, which shows high electrocatalytic activity on the I/I-3 redox reaction. A maximum power conversion efficiency of 6.78% is achieved for the DSSC based on the resultant CoS2 nanocrystal CE, which is close to that of the cell using a Pt CE (7.38%) under the same condition. Moreover, the flexible device based on a CoS2 CE exhibits an efficiency of 6.40%. The results indicate that the self-assembled CoS2 nanoctrystal film may replace the expensive Pt CE for DSSC application, especially for the large-scale flexible devices.