Effect of Different Graphene Oxide Contents on Dye-Sensitized Solar Cells

Graphene/TiO₂ composite films were deposited on fluorine-doped SnO₂-coated conductive substrates by spin coating acting as photoelectrodes of dye-sensitized solar cells. The graphene/TiO₂ composite films were characterized by scanning electronic microscopy, an X-ray diffractometer, a UV-visible spectrometer, and electrochemical impedance spectroscopy. Nyquist plots showed the decrease of impedance, in which electron transport rate was promoted. The photovoltaic properties showed that the incorporation of graphene could increase the short-circuit current density and photoelectric conversion efficiency. However, an excessive incorporation of graphene led to the enhancement of charge recombination and the reduction of photoelectric conversion efficiency. The graphene/TiO₂ composite film with 1.5-mL graphene oxide solution obtained the optimal photoelectric conversion efficiency of 5.26%.