Fabrication and characterization of electrospun carbon nanotubes/titanium dioxide nanofibers used in anodes of dye-sensitized solar cells

Electrospun carbon nanotubes/titanium dioxide (CNT/TiO2) nanofibers, used as anode material for dye-sensitized solar cells (DSSCs), were fabricated using a mixture of titanium isopropoxide, multi-walled carbon nanotubes (CNTs), and polyvinylpyrrolidone (PVP) in dimethylacetamide. The CNT/TiO2 nanofiber-based anodes of DSSCs were prepared by electrospinning the precursor solution directly onto fluorine-doped tin oxide substrates containing different amounts of CNTs (mass ratio CNTs:TiO2 = 1, 5, 10, 20 wt%). After calcination at 500 °C in air for 2 h, the porosity of these nanofibers increased with increasing amount of CNTs. The effect of the CNT content in the CNT/TiO2 nanofiber-based photoelectrodes on the photovoltaic properties of the resulting DSSCs was investigated. The power conversion efficiency (PCE) of the DSSCs was increased, thereby exhibiting an increase in the rapid electron transfer and suppression in charge recombination owing to the presence of CNTs in the CNT/TiO2 nanofibers. The maximum PCE of 3.39% was obtained in the presence of 5 wt% of CNTs in the CNT/TiO2 nanofibers. However, when the CNT content in the CNT/TiO2 nanofibers was more than 5 wt%, the PCE was rather decreased, which indicates that an excess amount of CNTs in the CNT/TiO2 nanofibers interfered with the electron transfer and increased the rate of charge recombination.