Interface Functionalization of Photoelectrodes with Graphene for High Performance Dye-Sensitized Solar Cells

The microstructures of photo- and counter-electrodes play critical roles in the performance of dye-sensitized solar cells (DSSCs). In particular, various interfaces, such as fluorinated-tin oxide (FTO)/TiO2, TiO2/TiO2, and TiO2/electrolyte, in DSSCs significantly affect the final power conversion efficiency (PCE). However, research has generally focused more on the design of various nanostructured semiconducting materials with emphasis on optimizing chemical or/and physical properties, and less on these interface functionalizations for performance improvement. This work explores a new application of graphene to modify the interface of FTO/TiO2 to suppress charge recombination. In combination with interfaces functionalization of TiO2/TiO2 for low charge-transport resistance and high charge-transfer rate, the final PCE of DSSC is remarkably improved from 5.80% to 8.13%, achieving the highest efficiency in comparison to reported graphene/TiO2-based DSSCs. The method of using graphene to functionalize the surface of FTO substrate provides a better alternative method to the conventional pre-treatment through hydrolyzing TiCl4 and an approach to reduce the adverse effect of microstructural defect of conducting glass substrate for electronic devices.