Electrophoretic graphene oxide surface passivation on titanium dioxide for dye sensitized solar cell application

A dominant interfacial recombination pathway in the dye sensitized solar cell (DSSC) was suppressed by coating graphene oxide (GO) on the titanium dioxide (TiO2) nanoparticle layer via the electrophoretic deposition (EPD) method. DSSC utilizing 5 min coating of GO by EPD on TiO2 nanoparticle layer showed 5% enhancement in the photo-conversion efficiency (from 5.7% to 6.0%), and 5% enhancement in the short circuit current density (from 11.4 mA/cm2 to 12.0 mA/cm2) in comparison with reference DSSCs which did not use GO on TiO2. GO coating on TiO2 is attributed to the efficient suppression of the photo-generated electron–hole recombination at the TiO2/dye/electrolyte interfaces. The further increase in the thickness of GO (10- and 20-min EPD coating) on the TiO2 nanoparticle layer impeded the charge transport as the performance of the respective DSSCs was significantly affected. It suggested that the probability of photo-generated electron tunneling from dye to TiO2 was suppressed by increasing the thickness of the GO layer. Presented results assure that GO can be considered as a competitive surface passivation candidate for nanostructured excitonic solar cells.