Hybrid graphene/metal oxide anodes for efficient and stable dye sensitized solar cell

Abstract We report the effect of incorporating graphene microplatelets into a SnO2–TiO2 mesoporous heterostructured anode, to enhance the efficiency and long-term stability of dye-sensitized solar cells (DSSCs). DSSCs were fabricated by introducing different concentrations of graphene microplatelets (up to 0.50 wt%.) into the SnO2–TiO2 mesoporous network. At an optimized concentration of 0.03 wt% of graphene microplatelets, the highest photoconversion efficiency (PCE) of 3.37% was achieved, which is ∼16% higher than the one measured for control devices made with standard SnO2–TiO2 anodes. This improvement of PCE can be attributed to enhanced electron lifetime and reduced charge recombination in the hybrid SnO2–TiO2/graphene heterostructure anodes, confirmed by transient photovoltage decay and electrochemical impedance spectroscopy. Improved dye loading in the SnO2–TiO2/graphene anode was confirmed with UV–Vis–NIR spectrophotometry. In addition, we recorded long-term stability of the DSSCs for 200 h of continuous illumination under one sun simulated sunlight (AM 1.5G). Our investigation demonstrated that the addition of graphene microplatelets (0.03 wt%) in the anode, shows superior long-term stability exhibiting a mere 8% PCE drop, while a sharp plummet of ∼30% in PCE was observed in control devices. These findings signify that the SnO2–TiO2/graphene heterostructure architecture is a promising anode towards efficient and stable DSSCs.