Co-sensitization of graphene/TiO2 nanocomposite thin films with ruthenizer and metal free organic photosensitizers for improving the power conversion efficiency of dye-sensitized solar cells (DSSCs)

•Efficiency of DSSCs has been increased by employing co-sensitized nanocomposite thin films as photoanodes.•TiO2/N719/RK-1 based DSSC showed PCE of 8.45%, superior to that of individually sensitized DSSCs.•Nanocomposites of TiO2 and graphene (GR) have been prepared by varying the composition of GR from 0.05% to 0.2%.•TiO2/0.1%GR nanocomposite film sensitized with optimized N719/RK-1 solution showed the PCE of 9.45%•Increase in PCE can be attributed to improve light absorption and improve light harvesting efficiency.