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

Abstract

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 (R_ct) 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 (η) of 7.25% under 100 mW cm⁻² light intensity, which is comparable to that of thermally deposited Pt based DSSCs (η = 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.