Optimization of efficiency in dye-sensitized solar cells by the infusion of graphene to photoanode

Abstract

This research studies the influence of added graphene on the structure and performance of DyeSensitized Solar Cell (DSSC) photoelectrodes. For this purpose, a series of TiO₂ multi-layer photoelectrodes were fabricated by infusing graphene into each layer at a time to all six layers. A colloidal paste prepared by mixing TiO₂ nanoparticles (13 nm) and 0.1 M HNO₃ was spincoated on a clean FTO glass substrate to prepare the layered photoanodes. Graphene (SigmaAldrich) at 1 w% in relation to the TiO₂ was added to the colloidal suspension to prepare the graphene-added Nanocomposite layers of the multilayer photoelectrodes. The TiO₂electrodes were sensitized with dye N719 and were combined with the Pt counter electrode and polyiodide-based electrolyte to assemble DSSCs. The results indicate that the efficiency of cells depends on the layer to which graphene has been incorporated out of the six layers in graphenedoped TiO₂ photoelectrode. The graphene-doped photoelectrodes efficiency rise with the increase in the layer number which graphene doped and reaches the maximum value at the fourth layer. When graphene was added to the fourth layer, DSSC showed the best performance with the largest photoelectric power conversion efficiency of 6.99%, resulting in a 19.52% enhancement compared to the undoped photoelectrode-based DSSC (5.85%). The high transparency and conductivity of graphene significantly enhance the photoelectric power conversion properties of DSSCs. This enhancement occurs by improving the light scattering and conductivity of the TiO₂ layers and the electron transfer process from the dye molecule to the surface of the TiO₂ layer. However, the study continues to investigate the correct mechanism.