A composite counter electrode of CoS/MWCNT with high electrocatalytic activity for dye-sensitized solar cells

In this study, CoS coated multi-wall carbon nanotube (CoS/MWCNT) counter electrode (CE) was first incorporated into Pt-free dye-sensitized solar cell (DSSC). This composite film was fabricated using an electrophoresis of MWCNTs onto a fluorinated tin oxide (FTO) substrate and then subjected to CoS electrodeposition. The cyclic voltammetric tests recorded an enhanced electrocatalytic activity when the CoS was deposited onto the surface of the MWCNTs. Additionally, consecutive cyclic voltammetric tests demonstrated that the CE possessed excellent electrochemical stability. Thus, the DSSC assembled with CoS/MWCNT CE showed an enhanced photovoltaic conversion efficiency of 6.96% (compared to 2.91% for DSSCs with MWCNT CE or 5.86% for CoS CE alone) under full sunlight illumination (100 mW cm(-2), AM 1.5 G) due to the superior electrocatalytic activity of the out-shell CoS material and highly specific surface of the MWCNTs. Therefore, the CoS/MWCNT composite can be considered as a promising alternative CE for use in low-cost DSSCs. (C) 2011 Elsevier B.V. All rights reserved.