Novel platinum nanoparticles/vapor grown carbon fibers composite counter electrodes for high performance dye sensitized solar cells

A composite film composed of platinum nanoparticles (PtNPs) and vapor grown carbon fibers (VGCFs) was coated on FTO glass acted as a counter electrode (CE) for high performance dye-sensitized solar cell (DSSC) via a facially thermal approach. The PtNP/VGCF hybrid film was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TGA), X-ray diffraction (XRD), Raman, and X-ray photoelectroscopy (XPS). In addition, cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS) were measured to correlate electrocatalytic activity to photovoltaic performance of DSSCs based on these PtNP/VGCF hybrid counter electrodes (CEs). Results indicated that PtNPs can enhance the thermal stability of VGCFs and were uniformly distributed over VGCFs with high porosity to provide large exposed surface area for redox reactions occurring within the films. VGCFs were found to benefit Pt reduction during annealing at 450 °C. A DSSC comprising the hybrid CE with a weight ratio of PtNPs to VGCFs of 3:7 (PV37) illustrated a higher solar-to-electricity efficiency of 7.77% in comparison to 7.31% for a conventional Pt CE or 3.79% for a pure VGCF CE. Electrochemical analyses demonstrated that PV37 CE featured the strongest electrocatalytic ability for the reduction of I3− to I− and the lowest Nernst diffusion resistance, confirming the highest power conversion efficiency among the samples evaluated.