Facile synthesis of hierarchical nanostructured polypyrrole and its application in the counter electrode of dye-sensitized solar cells

Hierarchical nanostructured polypyrrole (HNPPy) of spherical polypyrrole (PPy) nanoparticles anchored on the surface of PPy nanofiber network is prepared by a facile process and incorporated into dye-sensitized solar cells (DSCs) as Pt-free counter electrode. This unique hierarchical nanostructure can provide the fast electron-transport pathway and abundant electrocatalytic active sites simultaneously. Electrochemical impedance spectroscopy analysis demonstrates that the electrocatalytic activity of HNPPy electrode for the I3− reduction is higher than that of PPy nanoparticles (PPyNPs) electrode and comparable to that of Pt electrode. As a consequence, the DSC fabricated with HNPPy counter electrode achieves a high conversion efficiency of 6.78%, which is close to the efficiency using Pt counter electrode.