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

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 similar to 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 the 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 similar to 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. (c) 2020 Elsevier Ltd. All rights reserved.