Hybrid TiO2-Graphene nanoribbon photoanodes to improve the photoconversion efficiency of dye sensitized solar cells

We report the effect of incorporating different loadings of graphene nanoribbons (GNR) into a standard photoanode made of TiO2 sensitized with dye molecules. The GNRs are observed to significantly improve the photoconversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). The TiO2-GNR hybrid photoanodes were prepared using the doctor-blade method. The presence of GNR in the composite photoanode was characterized by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Our results highlight that, at an optimum loading of 0.005 wt%, GNR increases the PCE of DSSCs up to values 20% higher than the PCE of control devices. This improvement is mainly attributed to improved dye loading, enhanced electron lifetime and reduced carrier recombination, as confirmed by quantitative measurements of dye loading, transient photovoltage decay and electrochemical impedance spectroscopy results, respectively.