Incorporation of Nanostructured Carbon Composite Materials into Counter Electrodes for Highly Efficient Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSSCs) composed of nanostructured carbon composite materials-stacked counter electrodes (CEs) were fabricated in the present study. As the potential replacement of expensive platinum (Pt) thin film, various carbon composite materials, including zero-dimensional carbon nanoparticles (CNPs), one-dimensional multiwalled carbon nanotubes (MWCNTs), and two-dimensional graphene flakes (GFs) as a suitable charge transfer medium were deposited on the surface of CEs using a screen printing process. As the results, CNPs were found to result in deteriorating the charge transfer from CE to liquid electrolyte due to the formation of highly aggregated structures with very low specific surface area. However, MWCNTs and MWCNTs-added carbon composites (e.g., CNP/MWCNT, MWCNT/GF, CNP/MWCNT/GF) were found to enhance the charge transfer from CE to liquid electrolyte due to the formation of highly networked structures with high specific surface area. The resulting PCE of DSSCs composed of pure MWCNTs- and MWCNTs-added carbon composites-based CEs were very similar with that of DSSCs composed of Pt-based CEs. This suggests that the nanostructured carbon materials especially composed of MWCNTs and their composites are one of the promising candidates to replace the expensive Pt in the CEs of DSSCs.