Conducting polymer coated non-woven graphite fiber film for dye-sensitized solar cells: Superior Pt- and FTO-free counter electrodes

Conventional platinum (Pt) or emerging materials for the counter electrodes (CEs) of dye-sensitized solar cells (DSSCs) have been fabricated on a fluorine-doped tin oxide (FTO) substrate. In this study, carbon paper with three-dimensional (3D) carbon fiber networks, which is highly porous, but has sufficient space for efficient transportation of electrolytes, is used in replace of the conventional heavy, rigid and expensive FTO/glass substrate in DSSC CEs. To prove the advantages of these highly conductive carbon paper electrodes, a thin poly(3,4-ethylenedioxythiophene) (PEDOT) film is uniformly coated on the surface of 3D carbon paper via a chemical polymerization method. The catalytic properties of the PEDOT/carbon paper as the CE in a DSSC are studied using cyclic voltammetry, J-V, and IPCE measurements. Interestingly, the PEDOT/carbon paper CE exhibits better functionality as a CE for tri-iodide reduction as compared to conventional Pt/FTO-based CEs. The controlled DSSC with a PEDOT/carbon paper CE exhibits a power conversion efficiency of 8.05% under 100 mW·cm^-2 illumination, which is higher than that of conventional DSSCs with standard Pt/FTO CEs (7.41%).