Incorporation of graphenes in nanostructured TiO2 films via molecular grafting for dye-sensitized solar cell application

This paper presents a systematic investigation on the incorporation of chemical exfoliation graphene sheets (GS) in TiO₂ nanoparticle films via a molecular grafting method for dye-sensitized solar cells (DSSCs). By controlling the oxidation time in the chemical exfoliation process, both high conductivity of reduced GS and good attachment of TiO₂ nanoparticles onthe GS were achieved. Uniform GS/TiO₂ composite films with large areas on conductive glass were prepared by electrophoretic deposition, and the incorporation of GS significantly improved the conductivity of the TiO ₂ nanoparticle film by more than 2 orders of magnitude. Moreover, the power conversion efficiency for DSSC based on GS/TiO₂ composite films is more than 5 times higher than that based on TiO2 alone, indicating that the incorporation of GS is an efficient means for enhancing the photovoltaic (PV) performance. The better PV performance of GS/TiO₂ DSSC is also attributed to the better dye loading of GS/TiO₂ film than that of TiO₂ film. The effect of GS content on the PV performances was also investigated. It was found that the power conversion efficiency increased first and then decreased with the increasing of GS concentration due to the decrease in the transmittance at high GS content. Further improvements can be expected by fully optimizing fabrication conditions and device configuration, such as increasing dye loading via thicker films. The present synthetic strategy is expected to lead to a family of composites with designed properties. © 2010 American Chemical Society.