Electrospun carbon nanofibers as low-cost counter electrode for dye-sensitized solar cells

Electrospun carbon nanofibers (ECNs) have been explored as an electrocatalyst and low-cost alternative to platinum (Pt) for triiodide reduction in dye-sensitized solar cells (DSCs). The results of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements indicated that the ECN counter electrodes exhibited low charge-transfer resistance (R _ct), large capacitance (C), and fast reaction rates for triiodide reduction. Although the efficiency (η) of ECN-based cells was slightly lower than that of Pt-based cells, their short circuit current density (J _sc) and open circuit voltage (V_oc) were comparable. The ECN-based cells achieved an energy conversion efficiency (η) of 5.5 % under the AM 1.5 illumination at 100 mW cm^-2. The reason for lower cell performance using the ECN electrode was because of its lower fill factor (FF) than that of Pt-based cells, probably caused by high total series resistance (R_Stot) at ∼15.5 Ω cm², which was larger than that of ∼4.8 Ω cm² in the Pt-based devices. Simulated results showed that the fill factor (FF) and η could be substantially improved by decreasing R_Stot, which might be achieved by using thinner and highly porous ECNs to reduce the thickness of the ECNs counter electrode.