A detailed investigation on the performance of dye-sensitized solar cells based on reduced graphene oxide-doped TiO2 photoanode

The sintered TiO2 nanofilms were immersed in the aqueous solution of graphite oxide and then were thermally reduced to reduced graphene oxide (RGO), resulting in RGO-doped TiO2 photoanodes employed in the dye-sensitized solar cells (DSSCs). This preparation method for the reduced graphene oxide-TiO2 (RGO-TiO2) photoanode could avoid the loss of RGO during the sintering process. The presence of RGO in the photoanodes was confirmed using Raman analysis, scanning electron microscopy, transmission electron microscopy, and energy-dispersive spectrometer. The amount of RGO in photoanode was obtained by thermo-gravimetric analysis. Other techniques such as X-ray diffraction, Brunauer-Emmett-Teller, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the composite materials of RGO-TiO2. The J-V measurement of RGO-TiO2-based DSSCs showed that the best photoelectric conversion efficiency (eta) of 6.85% is 11.7% higher than that of the pure TiO2 (P25-TiO2)-based DSSCs. It was shown that RGO in the photoanode could facilitate the phase transition in TiO2 crystals (from anatase to rutile) resulting in the mixed crystals in the photoanodes. The existence of RGO and mixed-crystal structure of TiO2 changed the electronic transmission pathway, reduced the recombination rate of electron-hole pairs, and thus improved the eta of DSSCs.