Dye-sensitized solar cells based on spray-coated carbon nanofiber/TiO2 nanoparticle composite counter electrodes

Electrospun carbon nanofiber (ECN)/TiO2 nanoparticle composite counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) were successfully prepared by spray-coating an ECN/TiO2 (1 : 1 by weight) mixture on a fluorine doped tin oxide (FTO)-glass substrate. TiO2 particles (Degussa P25) were used to bind carbon nanofibers and adhere them to the FTO-glass substrate. Electrochemical impedance spectroscopy (EIS) measurements revealed that the spray-coated ECN/TiO2 composite CEs have lower charge transfer resistance (Rct) and higher interfacial capacitance (Q) than those of Pt CEs. Cyclic voltammograms (CV) further indicated that ECN/TiO2 composite CEs have a faster tri-iodide reduction rate than those of Pt CEs. DSSCs fabricated using ECN/TiO2 CEs showed a power conversion efficiency (h) of 7.25% under 100 mW cm(-2) light intensity, which is comparable to that of thermally deposited Pt based DSSCs (eta = 7.57%). Moreover, ECN/TiO2 composite CE based DSSCs demonstrated almost equal power conversion efficiency to that of Pt based cells by adding only 8 wt% Pt, which unveiled a cost-effective alternative of costly Pt CEs in DSSCs.