Fabrication of high performance multi-walled carbon nanotubes/polypyrrole counter electrode for dye-sensitized solar cells

In our present study, the composite film of MWCNTs/Ppy (multi-walled carbon nanotubes and polypyrrole) was proposed as CE (counter electrode) catalyst in DSSCs (dye-sensitized solar cells) to speed up the reduction of triiodide to iodide. The MWCNTs/Ppy composite film was synthesized and fabricated it on rigid fluorine-doped tin oxide substrates by using a facile electrochemical polymerization route, and served as CE in DSSCs. The unique structural characteristics including rough surface consisted of the numerous MWCNTs coated on Ppy nanoparticles guaranteed fast mass transport for the electrolyte, and enabled the MWCNTs/Ppy CE to speed up the reduction of triiodide to iodide. The electrochemical analyses came from cyclic voltammetry and electrochemical impedance spectroscopy revealed that the MWCNTs/Ppy CE possessed more excellent electrocatalytic activity, electrochemical stability and lower charge transfer resistance of 2.82 Ω cm2 in comparison with a sputtered-Pt CE. The DSSC assembled with the novel MWCNTs/Ppy CE exhibited a high light-electric conversion efficiency of 7.42% under the illumination of 100 mW cm−2, comparable to that of the DSSC based on sputtered-Pt electrode (6.85%). Therefore, the MWCNTs/Ppy composite film can be considered as a promising alternative CE for DSSC due to its high electrocatalytic performance and excellent electrochemical stability.