Photovoltaic Efficiencies on Dye-Sensitized Solar Cells Assembled with Graphene-Linked TiO2 Anode Films

To promote the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs), graphene is introduced as a working electrode with TiO2 in this study, because it has great transparency and very good conductivity. XRD patterns indicate the presence of graphene and TiO2 particles in graphene-linked TiO2 samples. Moreover, TEM pictures also show that the nano-sized TiO2 particles are highly dispersed and well-linked onto the thin layered graphene. On the basis of the UV-visible spectra, the band gaps of TiO2, 1.0 wt % graphene-TiO2, 5.0 wt % graphene-TiO2, and 10.0 wt % graphene-TiO2 are 3.16, 2.94, 2.25, and 2.11 eV, respectively. Compared to pure TiO2, the energy conversion efficiency was enhanced considerably by the application of graphene-linked TiO2 anode films in the DSSCs to approximately 6.05% for 0.1 wt % graphene-TiO2 with N719 dye (10.0 mm film thickness and 5.0 mm x 5.0 mm cell area) under 100 mW/cm(2) of simulated sunlight. The quantum efficiency was the highest when 1.0 wt % of graphene was used. In impedance curves, the resistance was smallest for 1.0 wt % graphene- TiO2-DSSC.