Acetylene carbon black-graphite composite as low-cost and efficient counter electrode for dye-sensitized solar cells (DSSCs)

In this work, we investigated the morphology, electrical conductivity, catalytic properties, and binding energies of electronic states of a system consisting of acetylene carbon black (AB) and graphite as efficient and low-cost counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), where ratios of AB to graphite of 0:1, 1:3, 1:1, 3:1, and 1:0 were investigated. These carbon-based CEs were characterized using four-point probe conductivity measurement, field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NAXAFS), electrochemical impedance spectrum (EIS), and current-voltage (I-V) performance. Introduction of small AB particles into graphite paste enhanced the electronic conductivity of AB-graphite composite due to the bridging of the graphite flakes for electrocatalytic activity of triiodide reduction. AB particles also offer large surface area to provide high electrochemical performance in DSSCs. The overall highest power conversion efficiency of 5.06% was achieved for the DSSC fabricated with a CE consisting of AB-graphite ratio of 3:1, which is comparable to the DSSC performance with conventional platinum (Pt) CE. These findings suggest that AB and graphite composite could be a promising CE for low-cost DSSCs.