Economical and highly efficient Pt-free counter electrode for dye-sensitized solar cells

Fe-Co nanoparticle-incorporated carbon nanofibers ((Fe-Co)-CNFs) were obtained by a simple and flexible electro-spinning method and were further pre-oxidized and carbonized under a high-temperature nitrogen atmosphere for application as counter electrodes for highly efficient platinum-free dye-sensitized solar cells (DSSCs). Electrochemical characterizations revealed that the (Fe-Co)-CNFs showed excellent electrocatalytic activity for the I-3 (-)/I (-) redox couple. Photoelectric performance tests have shown that dye-sensitized solar cells equipped with (Fe-Co)-CNF counter electrodes have comparable photovoltaic efficiency to platinum counter electrode cells. This is because the graphite properties of these fibers rendered them electronically conducting. One-dimensional nanofibers provide oriented electron transport pathways, while lapped fibers form a three-dimensional mesoporous network, enhancing the contact with the electrolyte, and hence leading to faster ionic reaction kinetics. This study demonstrates that (Fe-Co)CNFs can be used as low-cost high-efficiency counter electrodes for DSSCs.