Effect of co-sensitization in solar exfoliated TiO2 functionalized rGO photoanode for dye-sensitized solar cell applications

In this report graphene oxide is successfully prepared by modified Hummers' method at room temperature without using low temperature ice bath reactor. For the fabrication of DSSC photoanode, rGO-TiO2 nanocomposite was prepared using a novel two step hydrothermal and solar exfoliation process. Formation of anatase TiO2 with tetragonal structure is confirmed using XRD pattern. Peak splitting occurs in Raman 2D band indicates the presence of bi-layer rGO. FESEM and HRTEM studies show the synthesized spherical shaped TiO2 nanoparticles embedded on rGO flakes and the average particulate size is found to be c.a 10 nm. FTIR and XPS results confirm the formation of direct bonding between Ti and C atoms in rGO-TiO2 by the observation of vibrational band at 1124 cm(-1) and binding energy at 284.13 eV respectively. DSSC devices are fabricated and EIS measurements are performed to determine interfacial charge transfer kinetics such as chemical capacitance, recombination resistance and electron lifetime. Here, we report for the first time the results on the co-sensitization of solar exfoliated rGO-TiO2 as photoanode using a combination of metal-free and metal-based organic dyes. Enhanced PCE of 6.9% is realized in N719 + N3 co-sensitized DSSC by its increased electron recombination lifetime.